Does Sucking Your Thumb Break Your Fast?
Question

I have an awkward problem, that is I still suck my thumb since I was a child! It can be quite extreme when I am not feeling too well. I am in doubt if this is Haram at all, and does it nullify my fast? I heard a friend say anything that enters the body nullifies the fast. Please answer my question a.s.a.p. because Ramadan is beginning soon and it is extremely embarrassing for me to talk to anyone about it, not even my husband!
Praise be to Allah.You have to try hard to give up this habit, and take your thumb out of your mouth every time you realize that you are sucking your thumb. Whatever happens because of forgetfulness will not affect your fast. 
The Prophet (peace and blessings of Allah be upon him) said: “Allah has forgiven my ummah for what they do by mistake or out of forgetfulness, and what they are forced to do.”
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And Allah knows best.