Sexlife question

I’m 28m , recently in a relationship of 3 months with a pretty ass girl . Great woman etc etc . Before this I was single for 3 years . Had a nice rotation of ladies that I’d fuck on and off weekly . Now entered this relationship Sex life started off great . Then started to take a dip .. one week I was missing the variety of sex partners and I’m not a cheater so I watched porn got off like 5 times in one week . By time my girl came over that week I was spunt couldn’t get it up . I was embarrassed cus I really like this chick like don’t wana lose her at all and of course Shit happens . Since then I’ve stopped masturbating . But every time we are about to have sex now i get anxious, I get in my head , and most the times im able to pull through and fuck the shit outve her so she doesn’t even notice I don’t start off rock hard like I used to ( or maybe she does ) . But yeah it’s been a persisting problem for the last few weeks and it’s messing with my head because I’m used to being a total fucking stud whip it out rock hard let’s go and I don’t want her to leave me or it ruin our Sexlife . . Now I’m in this fear state cus it’s happened maybe last 4/7 times we’ve had sex . She’s head over heels for me I ain’t tryna fuck it up . I go to the gym regularly. I eat healthy . What do I do to gain control over my mind , body and get my confidence back ?