I'm surprised your doctor didn't recommend an event monitor, which is a heart monitor you wear for a period of days or weeks. You hit the record button when you are experiencing the heart symptoms that are concerning you. You are correct - you do know your body better than anyone else and if you think something unusual is going on, you should look into it further. It may well be something harmless and it would give you peace of mind to know that. If these episodes are as predicable as you say, then it shouldn't be too hard to catch them on an event monitor and this will help your doctor figure out what is going on. On a personal note, late last year I began experiencing strange heart beats during sex. I have had ectopic ("skipped") beats and episodes of tachycardia all my life and these strange beats felt completely different. Then, at the first of the year, I had my first and so far only episode of atrial fibrillation, which is not as harmless as other types of arrthymias. The afib episode seemed to be adrenaline related. In my case, these strange beats during sex *may* have been a hint of the afib to come, but I can't say for sure. This doesn't mean anything serious is happening with you !!
Forgot one more thing. Although I do not feel weak. It does seem like my heart is struggling to beat sometimes. I can feel it most when I get up out of bed or a seat. It just feels like it's not working as it should, and struggling to beat properly.