Was it rape or am I simply ashamed?

This is something difficult to write, I often end up after sharing this story curl up feeling disgusted by myself. But it's been eating at me, whenever I try to have sex with partners now, I just go mentally distant and I want to know why.

When I was 16, I was having a lot of mental health problems - depression, bulimia, social anxiety and self harm. I used to go alone to a dance class where I met someone. We danced a lot together and chatted, he was a 48 year old man who lived on my route home. One day I agreed he could kiss me and he did. Then he started asking me up to his flat, which I did. I was a virgin, never dated and remembered thinking 'I will never get anyone, I'm too ugly for people my age'. He certainly took the lead in everything, but it was never aggressive. This ended up going on for months, he would tell me to wear low cut tops and push-up bras, what he did and didn't want me to do. I don't recall thinking about it at the time, I think at that point I was mentally numb. I can't recall when or why it stopped, but it did.

Any suggestions or thoughts are welcome.

i went out with men of around 38 at about 18 years old, and looking back at that, i can see a really distinct imbalance there.
i was naive in that sense, i didn't understand much at all about being taken advantage of, or that he was using me and didn't actually care at all.
i can see so many similarities in what you've written, and you were only 16.. barely out of school (if you'd left by that point even.?)..

according to the law where i am.. you can consent at 16.. but given how he manipulated and controlled you, i'd say it's clear that he took advantage, and you had no way of understanding just how to defend yourself against that.

you're not saying he forced himself upon you and you're not saying you didn't consent. reading between the lines, you appear to be saying that he took advantage of your naivety. but whilst that's not moral it's not illegal either. bad things happen to good people. you just have to accept that you knew no better at the time and stop trying to hold yourself responsible for something that you now wish hadn't happened.

Sorry that happened to you. I'm sure that relationship was very important to you at the time. It's difficult to realize later that it wasn't a balanced relationship and was abusive in terms of its effects on you, even if it can't legally be classified as rape or assault (unless it was statutory rape due to your being below the age of consent in your area). He could have valued you enough to care for you without the sexual demands he made. That would have been appropriate for your age difference. But it's hard to see that at 16.

As others have said above, maybe give yourself a break and don't blame yourself for this. Realize that it was a bad experience, which he should have been aware of, even if you were not. The going numb thing may be your expectation that the same thing is happening again (not really being valued by your partner). So maybe try to focus on other aspects of your relationships, to make sure that all the good elements are in place and that you're valued for who you are. That may start with valuing yourself enough to realize you deserve to be valued & loved just as much by others, and to be happy. If you are struggling with that, maybe some counseling would help to reinforce it in your mind.