Nipple question

Hi, I’m not sure how many DPO I am. My LMP was 7/31/18-8/5. My husband and I had to skip IUI this month because I had a hysteroscopy on cd 9. I have no idea when I ovulated or if I did. Anyways, I’ve been getting up to pee everynight at least once but usually twice! That’s so odd for me. It doesn’t feel like a UTI though because when I feel like I have to pee, I swear gallons of liquid come out (lol, sorry tmi). Also, tonight (cd 28) I noticed I have white blotches on my nipples that I’ve never seen before. It isn’t the areolas, but my actual nipples have white spots (not raised, and my boobs aren’t sore really... they are a little but I am expecting AF anytime now). I usually have a 28 - 29 day cycle. I tested two mornings (8/23 and 8:25?) but they were negative. I’ll test again in the morning.any other ideas as to by my nipples are discolored? I might go to the doc to get checked for a uti anyways so I can always ask her too. Thanks!