Do you know when you ovulated? Reason I ask is it may be longer than 14 days from the start of your cycle, so your first test may have picked you up being pg early. The 2nd HPT would show stronger cos you're further along.

I know what you mean by being scared of going for a scan and not seeing a heartbeat. When I was spotting, my GP sent me for a scan. I thought I was 5wk3d (from LMP), so didn't want to go, in case there was no heartbeat, which would have made me worry more. The heartbeat was there and I was dated at 6wks, so worked out I'd ovulated early. It may be the opposite for you.

Maybe move the scan out a week (or not have a dating scan). You already know you'll freak if you don't see the hb, so moving it out will mean you have more likelihood of seeing it and you can still get an accurate date.