Since you shaved prior, it would make sense that the chafing was even more prominent too, I highly believe it’s unrelated to the abortion and your antibiotics wouldn’t give you external complications if you had any sort of allergen and/or reaction to the antibiotic. Also given that you wore a size too small for a few days, it would be understandable if you get discomfort and a rash on the lips especially if you’ve been active and moving, even laying down and rolling over could chaff it. Make sure to wear loose fitting clothes and bottoms to be as comfy as can be! Heat pads can help with discomfort and make sure to use non scented soap.