Giving head with TMJ

So I have TMJ, it’s a jaw thing. Haha, it might be best to look it up if you don’t know what it is. Anyway, i love sucking dick but my boyfriend is bigger than what I’m use to and every time I start sucking his dick, within 10-15 minutes, my jaw starts to hurt and there’s a high chance it could open lock. I hate that I can’t give him head because of the chance my jaw will open lock. About a week or two ago, I was sucking on his nuts for a long period of time, and my freaking jaw open locked. I was able to unlock it myself (thankfully).

Does anyone have any tips or have TMJ and can help me out?