MEN PLEASE HELP.. Casual Relationship that wont end?

Meet a guy last summer 10 years age difference, Been in a casual thing for over a year now.. initally had few dates he said he didnt think we were suited, we socialise in same town run into each other a good bit, He then started texting me ended up with each other ( i didnt sleep with him for about 6 months) this has been going on and off for the last year i have had few boyfriends in between but when ever im single he gets in touch, i recently meet another guy who is fairly straight fwd and Mr casual keeps texting i have always liked him enedeup meeting him 1 night recently he wasnt aware i had a boyfriend since then he has been texting all the time i just say im busy but feel so guilty cause am seeing nice guy, i text Mr casual yesterday ay been on a few dates n think gonna give it a go as feel we will only ever go round in circles maybe best not be in touch so much.. he replyed okay .. i feel bad towards him now but if he wanted to maybe make a go of things why didnt he say as i would have considered it?? I previosuly asked him few months ago and he said we were not suited. so i presumed he still felt same way.. maybe he does.. he was becoming more firendly and texting me every second day which he never used to do, i feel bad should i ask him straigh does he wanna make a go of things out or just leave it ???