I think that whether or not you want to engage in PMS should be
a personal choice and not a moral obligation. Ultimately, it should
be entirely up to you whether or not you want to allow him access
to your intimacy.
Be prepared, however, for the emotional turbulence afterwards
because it has been shown that women tend to get more emotionally
attached to her partner after engaging in intercourse (especially
the first time) and being young as you are, neither you nor your bf
may be prepared for your increased emotional dependence on him
afterwards.
