Sex slowing down

Hi,

I (27M) am in a 4 year relationship with my girlfriend (27F). When we first started dating I was concerned my libido would be too much for her. We agreed that having sex 3 or 4 times a week would be ideal (I’d like even more) but the longer we’ve dated the less it’s become.

I’ve brought this up a few separate times and each time it’s more or less blown off as of she’ll try for more. She works a demanding job as do I, and most of the time the claim is that she’s too tired. At first I thought maybe I’m just not pleasing her enough, but every time we have sex she orgasms and talks about how enjoyable it was after the fact.

I really don’t know what to do. I would never cheat on her, and everything else in our relationship is solid, but this aspect is becoming too much for me. We’ve had sex twice in the past month and at this point I’m more worried that if we had kids etc. that amount will only continue to decrease.

She has mentioned at times that she wants to spend quality time with me and that the time we spend having sex is not quality time together, but I disagree. We do spend quite a lot of time outside of physical intimacy together, and it irks me that sex is not “quality time”.

Am I wrong for terminating a relationship for lack of sex? I don’t feel I’m asking for a ton, and it bothers me knowing I was able to have a lot more sex when I was single than in a relationship.