Boyfriend keeps refusing sex

Hi, I am new to this forum and I signed up hoping I could get some advice here :) (sorry for the long post)
My boyfriend and I have been together for a year and a half and we’ve lived together for most of our relationship. Before getting together we were very close friends and I’ve known him since 5 years now. We’re in our early 30s and both work at the same university and have demanding jobs.

Our relationship started pretty fast and there wasn’t much dating and courtship, I guess also because we had known each other already.
In the first three months of our relationship we had an active sex life with amazing sex 4-5 times a week. I have a pretty high libido and I like to initiate things and he was very responsive and also initiating himself.

However, some 4-5 months into our relationship, things started changing. He wasn’t that responsive anymore and started refusing to engage in any sexual practices. At first I thought that he was tired and stressed out. However somehow I would always find some time for cuddling and for sex, but he kept refusing either because he would be late for work or because he was too tired. Ultimately we started developing a routine, we would only have sex on the weekend, and at most once a week. It would always be the same day, and it would always be in bed. Needless to say, this routine was killing all my appetite.

So I confronted him and listened all my complaints and he said he understood. I told him I don’t see myself having such a predictable sex life, and I asked him to try to change something and at least let himself be seduced and be less rigid (no pun intended). Moreover, I asked him why he was refusing me and why he didn’t initiate more often. He kept saying he found me attractive, but that he didn’t feel like having sex that often. We had our first serious discussion last summer. Ever since then, things haven’t changed much.

In my past relationships I had a very good and active sex life, with lots of fun and playfulness. In this relationship I also tried a little creativity. I proposed we would go home over lunch break for a quickie or have a sexy date one evening and then go home and continue in bed. I tired sleeping naked next to him, I tried wearing sexy lingerie, I tried talking dirty, I tried talking sweet, I proposed watching porn together, I proposed masturbating in front of each other, I even proposed buying some simple sex toys and try them out. No matter what I tried it mostly turned out awkward with him smiling and starting a conversation on a totally unrelated topic.

I don’t know what to do anymore. In the past few months I stopped initiating anything because I know I will be turned down. So I have to wait for him to initiate, which makes me feel totally powerless. I confronted him again about this, he said he saw my point, but he hasn’t changed anything.
I used to consider myself a very attractive woman and I could seduce all my past boyfriends every time I wanted to. Now I don’t know what to do anymore.

Has anyone been there? How did you sort things out? What else could I try?