Your boyfriend has committed rape which is an offence under Section 376 of the Indian Penal code. For the offence of rape, it does not matter that accused had sexual intercourse under the influence of drugs. Furthermore, it is also immaterial that accused and victim have had consensual relationship in past.
Absence of consent of the victim in alleged sexual intercourse constitutes offence of rape. If that consent victim was taken by the accused either by force or deception, then again it amounts to rape. Your case is strong enough to punish the culprit.
Therefore, you should immediately lodge a first information report against your boyfriend. Medical examination of victim is not mandatory at the time of lodging FIR. The statement of victim is enough to initiate criminal proceedings against the accused.
If you have any message from your boyfriend in which he had confessed his guilt, you should adduce those messages along with the FIR.