How Do I Tell Him About Mental Health Stuff If I'm Not Sure?

So I can usually keep my anxiety/depression under wraps pretty well. I haven't seen a therapist in several years.

Back in December I experienced 2 family deaths right after finals, and since then my depression/anxiety started to affect my sex drive. Not having sex started to really affect my relationship.

In high school and early college I made some bad decisions with guys, and some of those sexual experiences were traumatizing, and those flashbacks are affecting me now. I have no clue how to tell my boyfriend of 2 years that my low libido really isnt him, it's me.

help?