My bf is an INTP and very emotionally blocked. It was fine with me for a quick minute, but now it's starting to strain the relationship a bit.
Should I just ask him to try to open up a bit more, or wait it out a little more? (we've been together for about 3 months)
Been there, done that. Note though that for most INTPs, 3 months is still very early and this is usually the stage where they take a step back and begin analyzing their feelings towards you. I say give it more of time.
My advice to you is for you both to try to find a middle ground:
1) You need to understand his "love" / "feeling" language and expression will always be different. It will require for you to not be needy and be patient as your INTP gets comfortable with his relationship with you and as he processes his feelings.
2) He needs to make an attempt to be more emotionally expressive -- and the only way he would know that he needs to do that more is by you expressing in a gentle, non-accusatory manner your Fe needs, i.e., "Hon, I like it when you tell me [insert Fe comment] because it makes me feel [insert]."
Relationships are hard, and requires continuous communication and a healthy sprinkling of Fe to sustain/grow. Moreover, the essence of love defies logic, hence INTPs aren't necessarily ready-made, proficient partners off the bat. This is sometimes very hard to accept for the INTP's partner since the relationship could sometimes feel like a one-sided relationship or rather empty/lonely.
Its good to be patient but also recognize your needs / limitations. Relationships though (regardless of type) will only work if both partners wish to grow together. If he's not making an effort or leaving you unsatisfied, perhaps it isn't the relationship for you.