<s>[INST] I have been described Flucloxacillin as I found a lump on my right breast beside my nipple which was quite worrying. I am 20 years old 5 ft 7 and a healthy female. My doctor said it can be trapped fluid or trapped milk. I had a baby girl 18 months ago but dont think its that. Very worried. Anyway the antibiotics are making me feel sick dizzy and faint. Can someone help me what this is? Thanks [/INST] Welcome to Chat Doctor .1. Yes, your doctor said is true, generally seen after lactation.2. But before you take any medication, I would suggest an ultrasound breast get done to confirm that the lumps are the dilated ducts.3. The ultrasound will evaluate the consistence of the lump (ductal dilatation/cystic/solid)4. Also seen in the hormonal changes.5.first get it evaluated and can be treated accordingly. Anything to ask ? Do not hesitate. Thank you. </s>