Is this how jealousy feels?

i've never felt this way before, i'm not a jealous person but it feels so weird. here's the situation. my boyfriend and i are on a break. things were bad. we were getting annoyed by each other, and we decided to take a break. today i seen him talk to some lady, i didn't think nothing of it because she looks old enough to be his mom. i went home to go on facebook and i find out he was talking to the same lady on face book, flirting with her, and calling her babe! and the old hag was flirting back, ugh! i felt this weird burning sensation at the pit of my stomach that radiated to my chest. is this how jealousy feels? or am i just plain upset? what should i do about this? we were just on a break. how could he do this to me? i'm not seeing other people!