Giving head

Okay so my fiancé is the only person that I have been with sexually so he’s pretty much had to teach me everything. I want to get better at giving him head but I have TMJ so my jaws always hurt SO bad just minutes into it. I feel bad because I really want to make him feel good but I can’t do it for to long because my jaws will hurt so bad that I would cry. Any tips on how I can get better at it or something to make my jaws not hurt as bad??