Is stress a factor to a man's libido?

**TL;DR;**

I (24/F) have been dating my boyfriend (29/M) for over a year. We used to have a very active and interesting sex life. We would frequent it a few times a week. Now, we do it maybe once a month. I have initiated so many times, where he has shut me down with 'Im tired'. I can't understand what the change is and if I am the problem or not.

He has gone through major stresses at work and I do know that he has been under a lot of pressure. But I can't see how this has made he's sex drive completely non-existent.

Am I wrong for not being understanding that he just is stressed out or is he gaslighting me ?