Welcome to the Health Care Magic
rather vague briefing to suggest possibilities!
'No blood clots' is really re-assuring.
You have not mentioned you are taking penicillin (500 mg ??!!) - but suspect it to be a cause... Have you taken it before and did you have problems? Why penicillin? - do you have an infection? - that can cause the pain...Pain usually is not a side effect of penicillin.
It could be from Anxiety
You are overweight
- are you taking any other medicine that could affect?
are the common drugs that cause calf pain...
See you GP again - you will need physical examination and evaluation of all the drugs.
Wishing you speedy recovery