Is It Mandatory in Islam to Change Bed Sheets after Intercourse?
Question

I got married recently. I will be with my wife in bed (I mean intimately). The bed spreads might contain some sexual fluids. My question is should we change it every time that happens. We do change it now. But the problem is we are in a joint family (living with parents & brother) and it's kind of awkward to keep changing it often and washing the dirty ones.
Should we change the dirty ones? What happens when one sits on that? Should he or she do Ghusl or wudu to become clean again?
Praise be to Allah.If the fluid which is emitted is as a result of foreplay and what gets on the bedclothes is Mani (sperm) that is not mixed with any other secretions, then you do not have to wash the bedclothes because Mani is pure according to the correct scholarly opinion. 
But if what gets onto the bedclothes is Madhi (prostatic fluid) or some other secretion that comes from the private parts of the man or the woman, then you must only wash the spot where this fluid got onto the bed, because these secretions are regarded as impure. 
With regard to doing Ghusl , this is required in two cases: 
·         When intercourse takes place, which is when the entire glans (tip of the penis) enters the woman’s vagina, even if he does not ejaculate. In this case Ghusl is required of both the man and the woman, because the Prophet (peace and blessings of Allah be upon him) said: “When (the man) sits between the thighs and calves of a woman and the two circumcised parts touch, then Ghusl is obligatory.” (Narrated by Al-Bukhari, 291 and Muslim, 349). According to a report narrated by Muslim, “… even if he does not ejaculate.” 
·         When sperm is emitted without intercourse. If a man or woman reaches climax, then Ghusl is obligatory. If the man reaches climax but the woman does not or vice versa, then Ghusl is obligatory because of what has been emitted from them, because Allah says (interpretation of the meaning): 
“If you are in a state of Janabah (i.e. after a sexual discharge), purify yourselves (bathe your whole body).” [Al-Ma'idah 5:6]
Ghusl becomes obligatory when something is emitted or climax is reached, even if intercourse does not take place, and it becomes obligatory when intercourse takes place even if there is no ejaculation or climax, and it becomes obligatory when both take place together. 
And Allah is the Source of strength. (See Fatawa Al-Lajnah Ad-Da’imah; Shaykh Ibn `Uthaymin, Kitab Fatawa Al-`Ulama’ fi `Ishrat An-Nisa’, 36, 42; Fatawa Manar Al-Islam, 1/110)
And Allah knows best.