Being in a state of major ritual impurity (janaba) does not invalidate one’s fast. The scholars explicitly mention that if one remained on this state for the complete duration of the fast, namely from Fajr till Maghrib, the fast would still be considered valid. [Shurunbulali, Maraqi al-Falah]
However, delaying the ritual bath (ghusl) may be contrary to what is best. It is not perse sinful to continue sleeping after experiencing a wet dream. However, if delaying the ritual bath leads to missing a prayer then it would be impermissible to do so.
Lastly, there is no need to wait until one has been to the toilet a few times before one performs the ritual bath. This is excessiveness and should be avoided. Rather, if one went to the bathroom merely once and then semen exited later (without any stimulation or a wet dream) one would be required to perform the ablution only, not a ritual bath (ghusl). [ibid]
