Boob rash

Hey ladies so this is my Second time getting this rash in between my boobs and under my boobs and It kinda itches it when I scratch it kind of burns but it I never ever get any darkness or anything under my boobs and I’ve always said to myself to wash under and between my boobs. I wash under my boobs really good when I’m in the shower and i literally make that my motto to have the skin under and between to match the rest of my skin and have no darkness so this is killing me because my hygiene is so important to me. But I’ve been sweating a lot lately and work a full time college student and i work all day so when i sweat in the morning while at school i do t have time to go home and shower because i have work right after and don’t get off until 9:30 pm and have class at 8am. but now this rash is here and I don’t know what it is. Do you?