Baby pooping a lot with mucous. Allergy?

My daughter (5 months old) is in top up feeding (breast milk + nestle Nan pro formula). She has cold (no cough though). She was pooping once in every 2 or 3 days till 2 weeks back. From last week she started pooping 5-7 times a day with a lot of mucuous. Doctor gave her a course of antibiotics and asked to start banana/rice and stop formula milk. We have started banana/rice, but could not stop formula as she screams her lungs out if we do not give her milk. She sucks on breast more than an hour, still ends up crying until we give her formula milk. The antibiotics are over now, but she is still pooping for 5-7 times a day, each time with a lot of mucous (not watery). Picture attached. We went to 3 paediatrician so far and each one says one thing. Is it because of cold or a stomach infection or milk allergy? Until last week formula milk worked well for her, so we are not sure. She does not have fever and active otherwise. Please advise.