Okay.. lots of issues here!
1. Ibuprofen does not cause weight gain. Ibuprofen tends to cause nausea, vomiting and can cause abdominal bloating and constipation. It has contributed to weight loss. It has lots of other potential side effects, but in the long list, weight gain is not one of them.
2. Ibuprofen (Nurofen) is not contraindicated in asthma - it is rather a "precaution". That's because it can trigger asthma attacks in some people.. as can aspirin. You can still take either of these, but talk to your doctor first.
3. If you stick to 8 or less tablets of paracetamol per day, you should be fine. If you experience side effects at this level, see your doctor.
4. Aside from paracetamol, aspirin and ibuprofen (or similar), there aren't any other over the counter pain relievers - you would have to see your doctor for a prescription for something.
All good? Any questions?