If you can get good firm erections by yourself, it’s likely there’s not a physical prblm, so it’s more likely a psychological issue. Relax - many of us have had issues like that, especially in a new relationship where you’re wanting everything to go perfectly, but it just doesn’t always work that way. In these matters, sometimes it seems the harder we try, the worse things get. You just need to be completely relaxed & ‘in tune’ w/ your partner & not focus on ‘performance’, which as I always say is a terrible term! Just take it slow, if erections seem ‘iffy’, put penetration aside for the moment & enjoy other sexual activities - manual, oral, mutual masturbation, etc. Then at some point you’re going to be at ease enuf to go for the full deal.
Also, since you’re both working thru issues, why not talk it out with her - in fact, she might appreciate a chance to talk out her stuff as well. Tell her you really like her & want to please her & let her know if there’s any issue, it’s not her fault. Being open & honest should put you both at ease - maybe after a little airing-out, you guys can even joke about it a bit & take the seriousness out of it. After all, this shd be fun for both of you, not work!
Finally, as GR says, just make sure your Diabetes is under good control - you’d wanna do that anyway, regardless of any sexual activity...
Best of luck & let us know how it goes...
Glad you are intimate again, that's a good thing. Is your diabetes under control? And glad you are getting healthier, not smoking anymore. Perfect and good for you! Definitely use birth control as pregnancy in a new relationship is obviously an issue as is std's and all of that. (not that she has those but you both want to be protected).
Have you had a physical lately? I'd do that just to make sure your health is in order. If it is and your diabetes is under control, then the thing about sex is that it is very mental. Are you anxious or stressed getting intimate after a long hiatus?