Middle aged guy. Taking zero drugs that would affect sexual performance either negatively or positively. Long time girlfriend who likes sex and can cum PIV. Recently the start is the same where my girlfriend spends a few minutes getting my cock good and hard. I enter and everything is fine. We are both having fun. Then for no reason I start to get floppy. And other times when I stay hard I just can never reach the edge to actually cum. We have also tried hand jobs and oral and the same things happen. Any advice?
Physical health. Pick up running or biking. A lot of erection issues are related to the cardiovascular system.
Talk to a doctor. Could be a sign of something more serious.