Premature and weak erection cycle

So over the past six months I have been struggling with premature ejaculation and sometimes an inability to maintain a strong erection. I am a healthy 21 year old. It has put some severe strain on my relationship with my girlfriend. I have been working on these issues constantly and have managed to fix the inability to maintain erections part, but I still really struggle with the premature ejaculation part. My sex life with my girlfriend has not always been very good as I was inexperienced and she had a number of bad sexual experiences before our relationship, so it has been a touchy subject from the beginning. I am 90% sure that my PE problem is mental, but I am really struggling to overcome it because of how it affects our sex life when it happens. Every time I cum early my girlfriend gets very upset (I do too) and it makes her not want to have sex for a month or so. This gap is easier for her because she has always had a lower sex drive and I understand where she is coming from, but I don’t know how I can come into sex more confident and less afraid if the end result is so certain. I have worked constantly on the physical aspects of PE and I am sure that physically I am ready to perform better. I have thrown out the idea of trying to have sex a little more often just to get over this mental block in my head, but she is not interested. I guess what I am asking is how can I be more confident about having sex despite the potential outcomes and without too much support from my partner. Once again I am not throwing my girlfriend under the bus here and I understand how this issue could be hard for her, but being realistic she has no interest or confidence in helping me with this issue, so I need to figure it out on my own, but I’m not sure how. Thanks for any advice

Hi,
I had a similar issue in my mid 20s and couldn't get hard. Turns out I was just stressed and it worked better after I took a break from my job.
Try seeing a specialist, they have lots of experience with these problems!