For one, working hard to become a better runner is a fantastic reason to wear spandex! :)
Perhaps it's time to leave the HRM at home for a while and just go out to enjoy being out. Sometimes it's just TMI.
It could also be the antibiotics I think. Have taken 3 weeks and 2 days now so I think tonight will be my last dose. Fingers crossed!
(And it felt rubbish before I noticed how high the heart rate was at the end!)