I’m starting to hate my life because of my relationship

I (25M) and my girlfriend (23F) have been together for over a year. By far the best relationship I’ve ever had, everything is perfect. Except for one thing; our sex life. When we started dating we took literally every chance we got to have sex, which was perfect for me because I have a high sex drive. About 7 or so months in things started slowing down. We see each other 6 days a week. It went down to 5 times a week, then 4, 3, and now I’m lucky if we have sex twice a week. Often times we go a week or more without doing anything. We’re both in college, and work part time. If we’re seeing each other 6 days a week, I feel like having sex at least 4 of those days is reasonable. Ideally I’d like every day, but I doubt that’ll ever happen again. I’ve brought this up multiple times over the past several months, and I feel like nothing will ever change. I feel like I could tell her how much this is bothering me until I’m blue in the face and it won’t matter. She always has some excuse. I’m tired, I have a headache, I’m not feeling it, I’m depressed, it’s too hot, I haven’t showered yet, tomorrow for sure. Does tomorrow ever come? Fucking rarely. I’m not saying I condone it, or that I would ever do it, but I fully understand why so many people have a side piece. Jesus fucking Christ. I’m deeply unhappy with the way things are right now. I’m not sure how long I’m willing to give her to “get back to normal” for lack of a better term, but if things don’t change soon I think I wanna split up. Is that fucked up? I’m 25, and we have the sex life of people in their 60s and 70s. It’s making me genuinely depressed, I love this girl so much, and everything else in our relationship is perfect, but this issue is just too big to ignore. What would you do?