There are several statutes relating to Criminal Sexual Conduct in Minnesota. It would be possible for your boyfriend to be charged under one of these statutes. These statutes are very specific as to age (in terms of months). The statute that he might be charged under, and his possible defenses, will be determined by the number of months that you are separated in age.
The statutes provide that if you are under 16, and he is over 16, and he is more than 24 months older, it is felony criminal sexual conduct. It is indeed a serious charge that can involve possible prison time, and lenthgy probation, and predatory offender registration. If there has not been a lot of attention attracted to the situation, it is best to keep it that way. You should consult with an attorney in person and have that attorney on standby if charges are brought. I will say that there is often a lot of room for negotiated plea agreements that avoid conviction and registration in these types of situations, but much of that depends on the prosecutor and how well your attorney negotiates with them. DO NOT under any circumstances talk about this with anyone except a defense attorney, who has an obligation of confidentiality to you. Nobody else does, and any one of them could be close to law enforcement, or mandatory reporters like social workers, teachers, etc.
Alex De Marco