My guess is that you are both putting entirely too much pressure on your sexual response. The same thing happens to men who suffer from psychological ED. The more you think about it, the more you try to consciously will it to happen, the less likely it is to happen. instead of trying harder to orgasm, you counter-intuitively need to try less. After explaining to your boyfriend that your medication makes it more difficult for you to orgasm, tell him (and yourself) that you need to take a slower, more intimate approach to love-making. Lots of sensual touch, making out, oral sex, all of it without orgasm as a goal. You’re just going to enjoy the closeness of being together, touching each other, and making love. Honestly, this is how middle-aged and older people have sex anyway, because our bodies don’t often allow for the slamming, goal-oriented sex of our twenties. It can take longer to become aroused, and sometimes orgasm doesn’t happen at all, sometimes even for men. You’ve both got to learn to enjoy the experience for its own sake, and if orgasm happens, it’s a nice bonus.