I'm 18w preg, had amoxicilin for chest infection last month, this month on penicillin for bad throat infection, is it safe to take so many antibiotics?

Depends: If taking antibiotics for a bacterial cause then you are likely on the right path. When antibiotics are taken for viruses then the chance of side effects, resistance and reactions increase. Amoxicillin is safe for pregnancy otherwise. See your doctor for more answers.

Antibiotic usage: The antibiotics you have received are relatively safe with regard to potential complications, but all such decisions must be based on a risk/benefit assessment, and the best person to do that is your treating doctor. The overall level of health care in UK is among the best in the world. Listen to your doctor. Hope you are better soon.