Don't worry. Ds had constant ear infections so he was either on antibiotics or had a temperature for months on end. He had his 8 wks at 8 week. His 12 wk at 16 weeks They wouldn't do his 16 week in one go because of a history of bad reactions either, so he got his first set at 9 months, and his second set at 13 months.
He then had his 11 month one at 15 months and his MMR at 16 months.
Those were the first times we could manage where he wasn't already ill.
We're running about 4 weeks behind schedules on ours - no one's said anything negative about them (DD2 was in the middle of a nasty allergic reaction when the first set were due so we deferred them a bit since I figured I'd cut the poor kid SOME break!)