I started having sex later in life (mid-late 20s) and my first experience was very long. It lasted 4 hours with an erection the entire time and no ejaculation. I later had another relationship and had the same issue but over time I learned what worked for me to ejaculate during sex but then also started having trouble with having full erections and sometimes it would go limp after a bit of time (not 4 hours, but rather after 10 minutes or so). I was wearing a condom everytime I had sex up to that point in my life and I assumed the condom caused a lack of sensation. But I later had the same issues without a condom and while I did help not having anything on, it still felt as if I had a lack of sensation (like a shell was on my penis). It starts out fine during foreplay and goes limp shortly after sexual intercourse. It does help if the motion continues but any slow down or stop to change positions ruins everything.
I also have trouble getting full erections when masturbating using my imagination but I can become full and satisfied (regular ejaculation) when watching porn.
My second relationship was a bit emotionally abusive so I might have some mental issues from that (along with the porn watching) but I can't help but think masturbation is causing my sensation issues during sex. I assume my problems are not physical since I can climax on my own with visual help and it frustrates me. It has caused problems in my personal life and I don't know what to do to correct this issue.
How can I work on my esteem/mental feelings about this along with the sensation issue? Do I tell future partners about this from the start or just work it in if/when it occurs?
Any advice is appreciated.
Note: I have tried not masturbating for a while and that doesnt help much.
Thanks in advance for any advice.