You are certainly NOT a crazy over-reactive mama, you just want to know that things are okay. You were sent conflicting messages by the different triage nurses, and now you probably feel left in limbo while waiting for your next appointment. I can totally understand that!
I do think it's reassuring to hear that spotting can be expected sometimes after sex.... and that some of the mamas in the group have also experienced some significant RL pain..... but the bottom line is that only you know your body, and even if the last triage nurse felt like there were no big red flags, you deserve comfort and reassurance/support to set your mind at ease. I think you're doing the right thing by following up with MyChart messages and/or calling.
Also-- maybe that full/achy feeling over your uterus is actually your uterus and the baby stretching out. For a few weeks I was waking up after a night and I'd find my belly/abdomen to be very sore. I've started using more pillows to support my body in a better position, and that has helped quite a bit.
Any way, still thinking of you and sending good thoughts. Keep us posted.