Most people with inflammatory breast cancer will have several, but not all, of the many symptoms associated with IBC.  Usually the symptoms escalate rapidly, so the off and on nature of the aching in your breast makes is less likely that the problem is IBC.  You can read more about some of the rashes that have symptoms similar to IBC in this article.  Most rashes are not IBC, so your OB's advice to watch and wait is not unreasonable.  However, since the symptoms are still there, go back and be assertive about getting a proper diagnosis.  If she thinks the problem is skin related, ask for a referral to a dermatologist.  If she thinks it's an infection, an antibiotic would be appropriate, but if it does not work, don't mess around with multiple courses of antibiotics.  Ask for a referral to a breast specialist.  This probably will turn out to be a minor problem, but don't take any chances.  Good luck with the diagnostic process.