Partner doing so much overtime

So lately my partner has been getting to work atleast 45mins before his shift starts and its almost every second day he has to do overtime. I get a gut feeling he always stays around to flirt with other women there. Am I over thinking this?

As 2 months ago an old co worker come to the country town where we moved to an he lied to me about meeting her outside of work i found a message in his phone that night.