My girlfriend and I have been together for a few months now, and when we first started having sex, l used to last much longer— around 30-45 minutes of penetration alone.
My girlfriend would even get tired, and we'd take breaks. At first, we used condoms, but then she got on birth control, and I was still able to last long enough to make her cum multiple times through penetration (which is the only way she can orgasm). About 10 days ago, we said "I love you" for the first time, but now, l've suddenly started struggling to last longer than a minute during penetration.
I always focus on giving her oral and making sure there's lots of foreplay, but she can only cum through penetration, but lately, when it comes to actual penetration, I find myself finishing within a minute. We didn't have sex on Sunday, and last night it was worse-l came within 5 pumps, about 5 seconds in. I wanted to go for round two, but she was tired and wanted to sleep. I was more embarrassed and ashamed than l've ever felt. She told me it was fine, but it's obvious she hasn't cum in about 8 days, even though we've had sex four times in that span. I genuinely care about her pleasure, and I don't watch porn or masturbate.
I'm super stressed and haven't been able to sleep because all I can think about is why this is happening. I've even thought about going back to condoms for a few days to try and retrain myself. I want to get my "powers" back and feel confident in bed again, but I'm not sure what to do. My girlfriend even joked about me taking Viagra, which just made me feel worse, even though I know she was kidding.
I am not fat, I workout, I do cardio
I really need some advice-what can I do to improve?