You may have got yourself into a mindset where an orgasm is the 'goal' to reach, and the pressure this puts on you stops it from happening.
Why not decide from the outset that you are not going to try to reach an orgasm, and just see what happens. If you take the pressure off, you will really relax, instead of thinking you are relaxing.
Remember, sex is about loving and fun, it''s not a contest with a score at the end, for either of you.
When you feel comfortable, try stimulating yourself you will enjoy that, and so will he, it's a real turn on! You can attend to your most senstitive areas, and he can learn where they are, but remember - all fun, no pressure is the way forward.
No-one is going to give you a gold medal for climaxing - if it happens, great, if not, no big deal.