Petty jealousy or fair enough?

Its 4.18am and I'm still up after an argument with my partner of close to 7 years. We have a 4 year old son n live together. Recently I found his twitter account online after creating one myself. He had been saying things to this one girl like "when's the next bubble bath pic? :p " and " I bumped into you at the aus got talent event and u bumped my leg and I said u can keep it there if u like! :p" this girl is a local actress he met nothing more... I couldn't help but feel bit hurt n jealous. When I confronted him he got defensive and turned it around to be my fault. He was hostile... Was It fair enough of me to be upset?