Nipples...

So... I hardly wear a bra because it's summer. I just wear one when I'm going out or people come over. So anyways, my nipples have been very irritated just like that also when I touch them. I was taking a shower and I noticed some white stuff coming out of my right nipple. I'm really worried. I don't know if my nipple is irritated because I'm not wearing a bra. I don't think I'm pregnant because I haven't had sex. I've fooled around but never had sex. Sooo what do y'all think it is...?