Nipple question

When pregnant is it the nipple or the outside the nipple that gets bigger??? Mine seem massive and also my af's are between 28-31 days only one time that was 37 days that was because I was stressed also CD24 I had pink tinge on the 1st aug but that was it I don't use opk's but according to the period app that I use I ov on the 24th as that day I had backache acne on the 1st nothing since took hpt's BFN n on the 22nd 25th n 31st July dtd could there be a chance I could be pregnant fertile time was 19th-25th July my boobs hurt been when I'm lying down