Pleasant feelings/Unpleasant feelings & craving/aversion In dependent origination after sense-contact occured, craving is the next condition, which in turn forms attachment at its basis and so on...

Suppose I am eating something or taking a massage to get rid of pains, is this pleasant vedana immediately connected with craving?

Similarly with unpleasant feelings; Suppose I have a bike accident and I fall down the ground and my immediate reaction is: "Arghhh", and no other cursing; Is this considered aversion to unpleasant feelings?

Furthermore, if I go to toilett to take a pee is this good feeling connected with craving?

It seems to be quite difficult to discern whether one feels pleasant feelings (vedana) without craving,  pleasant feelings with craving &amp; the same with unpleasant feelings &amp; aversion.
Short Answer:

When you think "it would be nice to have more(/less) future contact with object X" - then you have craving; when you think "this feeling is (un)pleasant and it came from object X" - then you are creating/sustaining potential for future craving; and when you think "this feeling came from the mind, it is empty, dependently originated, transient, ephemeral, unreliable, like a phantom - therefore craving to have more(less) of it would lead to suffering, and instead I keep training the mind of suchness." - then you don't have craving nor do you create/sustain potential for future craving.

Long Answer:

It is a popular misunderstanding of Dependent Origination -- to assume that it describes a process as it unfolds moment-by-moment. No, it does not. Instead, according to Mahayana (esp. Karma-Kagyu lineage), it describes a logical sequence of stages of development of individual mind.

The "contact" described in D.O. is not the momentary contact of sense organ with an external stimulus. It is a stage of development of individual mind when "contact with an object" is delineated, designated, and recognized.

Then, Vedana described in D.O. is a stage when "feeling that comes from contact with an object" is delineated, designated, and recognized.

Once this stage is reached, "Craving for feeling that comes from contact with an object" has a basis to develop on.

A more detailed description of this phase (vedana => tanha) is given e.g. in MN 18 as vedana => sañña => vitakka => papanca.

In other words, as one learns to separate the feeling that comes from contact with an object from the experience of contact itself, one learns to formulate ideas like: "it would be nice to have another contact like that, to bring that feeling again" or "it would be nice to avoid a contact like that, to not bring that feeling again". Eventually, such an idea gets simplified to something like: "It's nice and I want it" or "It's bad and I don't want it".

Then, holding such idea, mulling over it, and pursuing it in practice - making it one's goal and one's mode of operation - is what's known as upadana or grasping.

Suppose I am eating something or taking a massage to get rid of pains, is this pleasant vedana immediately connected with craving?

As I said, D.O. describes the development of mind in general, not one particular instance. So, most of the time, experience and craving do not follow one another immediately. Instead, most of the time craving occurs on the basis of remembering some past experience.

But generally speaking, when you're eating something or taking massage, and at that moment you experience a pleasant feeling, if you attribute that feeling to the external object, thinking "this food gives me the feeling" or "this massage gives me the feeling" - then, on the basis of this attribution, your thinking about that experience in those terms will fuel and sustain the potential of the future craving towards that object (food or massage).

If on the other hand, you think "this pleasant feeling is born in the mind, is a product of the mind" and you think "this comfort is mind-made, empty, dependently-originated" or "this discomfort is mind-made, empty, dependently-originated" - then on the basis of thinking in these terms you will not fuel and not sustain potential future craving towards the object and will instead develop the mind of sufficiency in suchness.

It seems to be quite difficult to discern whether one feels pleasant feelings (vedana) without craving, pleasant feelings with craving &amp; the same with unpleasant feelings &amp; aversion.

In my Mahayana understanding, it boils down to your frame of reference, your attribution of experience to an entity. if you attribute pleasant/unpleasant experiences to what you think are "external" objects, then you will develop and sustain future craving to them - and if instead you recognize that all pleasant/unpleasant experiences are mind-made, empty, like phantoms - and learn to control your mind's frame-of-reference, your perspective, your interpretation - then you are not developing craving and are developing the mind of bodhi instead.

As for detecting the presence of craving in the here-and-now, if your mind is leaking to imaginary past or future and grasping onto an imaginary experience (whether positive or negative) - then that's craving/aversion right there. And if your mind is not leaking anywhere but is seeing things as they are, then that's a moment of suchness.

Here, I explained craving (leaking), the root of craving (attribution of experience to external objects), and path to cutting the root of craving (learning to reframe the experience in such a way as to no longer reify it as something real coming from the external objects and to instead think of it in terms of D.O. and 4NT). I explained it according to my understanding and in my own words. Hope it helps.