B..
I have had some Very serious bouts of mastitis (I'm talking a week or more in the hospital on IV antibiotics.) for years, before I was ever even pregnant. In fact, it went undiagnosed for a while, because doctors often treat it as a breastfeeding side-effect, and don't think a woman whose never dealt with pregnancy and breastfeeding can get it. Please do NOT wait. I speak from experience. You are at the point, that the infection is really starting to explode. Those red streaks (or spots, if you have those) are a bad sign, that the infection is advancing. Go to the labor and delivery ward and get on antibiotics. The first time I had a bout, I said I would wait until Monday (I had the red streaks and all.) and by Sunday morning I was in the hospital with breast being swollen 3 times it's normal size. I'm not trying to alarm you, but explain to you how fast it gets bad. don't wait, it's not worth it.
Like someone else said, if you wait...it turns into other things. My first infection also turned into cellulitis, staph, and almost went to my blood. Especially when pregnant, it's easier to treat early on. The longer you let it go (even just d days), the more chances for it to explode.
The ER doc told me red streaks on the skin are a BAD sign, that the infection is advanced and needs to be dealt with.