Firstly, I'm not a doctor so if you really think you are having heart trouble, please do phone the NHS helpline.
However, I also have health anxiety and have also have pains like you describe. From my reading of heart issues, I don pt think stabby pains are indicative of heart attacks. Your heart might race a bit because you are anxious though, so checking your pulse is not ideal. I got scrabbly pains too, (like someone had put a box of worms in my left breast) that was anxiety to I was given beta blockers. I rarely take them now but I needed them every night for a while, to stop the scrabbling feeling and let me get to sleep without worrying I was going to die in the night.
For the past year I have suffered HA. we had a health scare with DH. All fine in the end, but that worry put me on the path that we are all going to die, so now random aches and pains I get worry me.
I was also getting random breast pain, my oesophagus would spasm but I was convinced it was my heart. I did get an ecg at the clinic. All fine. I used to be scared to go to sleep as I could hear the pulse rushing through me ears! Now, i take acid reflux mess and most of my symptoms have stopped.
I can tell you that when my DH went away for a 2 day course, i got stabbing pains in my left breast that started almost as soon as he left the house. I used to get them a lot, but this was. Ore intense and more frequent. They only stopped because when I managed to get the bus into town to meet him off his train. I wasn't aware until later that that is when they stopped, but over dinner I realised I hadn't felt the pains for a while, and put 2 and 2 together.
Health Anxiety sucks. I've twice had to cancel events because the little pains in my head made me worry I had a brain tumour, I still worry about that but weirdly, when I'm not obsessed by it, I don't have pains. I take this as a good sign 😀 I've lost all enthusiasm for life and can't get interested in anything. I also worry too much about other people's health.
One thing that helps me is going for a walk. It is scary to go for a walk when you are worrying about your heart. So if you can go with a friend, please do. A nice walk along the beach or in a country park, somewhere that you can relax, but anywhere really, because along the walk, you will realise that you've not had any pain - you've been walking and talking and not thinking about your health. That realisation MIGHT bring on some pain again because you've started to think bout the pain, but it might be a comfort to realise that it's not constant, it's intermittent.
evwn at my worst, I never got pains during my driving lessons. Ever.
If you continue to feel pain, and are worried, ask your doctor for an ECG. Assuming all is good, it is amazing how much that can help you get back on track to feeling better about things. If you can discuss your anxiety too, he might give you medication - I got beta blockers which help.
Please please try not to worry. It's easier said than done, but if you get into a position or activity, where you've not had any symptoms for a while, that can have such a positive effect on your mental health.