After lots of conversation over months my husband and I decided a some months ago to open up our relationship more fully. I went on PrEP and we worked out our rules: must know where you are, can't interfere with "us time," no emotional attachments outside, etc. It's been a definite improvement for both of us.
Talking honestly is hard and it took us months to get there, but I encourage you to start the conversation. Have you asked him what he wants and if he's happy, lately?
If you're HIV negative and want to stay negative, I strongly encourage you to look into starting PrEP. (Your insurance WILL cover it.) And you should agree to get tested regularly (every 3-6 months) for all the other STDs. Oh, and you have been vaccinated against Hepatitis A and B, right?