Rash worries

I was due to have some dental surgery a couple of weeks ago but what with everything that's going on, this has been cancelled and my dentist gave me some antibiotics to make sure a small infection didn't get any worse whilst I waited. After a few days I noticed a rash had appeared on my stomach and a little bit on one thigh, actually was more like Petechiae than a raised rash but I didn't think much of it as my skin has been prone to stuff like this since starting BP medication with a diuretic last year. I finished the antibiotics 2 days ago and the rash has continued and spread on my trunk but is now less like Petechiae in most areas and more like a raised rash. Of course now I am panicking and googling and coming up with all sorts (you know the drill). The rash isn't itchy. I feel absolutely fine otherwise.

I can't see my GP at the moment because he is working only at the hospital right now. I could go to a walk-in clinic but I am not keen to do that under the present circumstances, especially as I feel otherwise well.

Logically I know this is more than likely to be connected to the antibiotics, especially when my skin is already very sensitive from the diuretics but of course I have wound myself up into a frenzy by googling. Also, the antibiotics ended almost two days ago and although the rash has faded a bit in the areas I first noticed, it has spread since then. I'm also connecting any ache or pain or vague symptom I've had in the past few months to this and I am in a right state.

If anyone can talk me down from this, I would be very grateful. It's the antibiotics, right?

Just to add, I'm never great on strong oral antibiotics and don't get prescribed anything with penicillin in any more but I've never had an actual rash before