Omg i freakin' hate facebook, why is he doing this? :(?

basically me ad my ex decided to get back together when im 18 which is this month :) ive seen him a couple of times since i finished my exams and they've all been really good. on thursday he posted on my facebook wall ''your so amazing <3 xxx'' and last night when i texted him he said ''he'd never felt this way about a girl before <3 '' it made me really happy becausee i love him with all my heart. But there's this girl on facebook whos forever posting love heart ''<3 '' on his wall, and more worryingly he starts it sometimes, like for example just now he posted ''<3 <3 <3 '' on her wall?! and she posted back saying ''<3 <3 <3 hubby xx'' i wanted to punch her in the face :( (sorry my emotions are running a bit high ) just two days ago he posted '' wifey <3 <3 <3 '' on her wall. i cant take it i wish she'd just f**k off! :( i dont want to have to care who she is, but because he seems to really like her how can i not?! iv'e been ignoreing this for a while thinking ahh they're just mates but this just now, pushed me over the edge and i dont know if its more serious?! i cant ask him only because i dont want him to think there's no trust :/ i dont stalk him on facebook i promise it's just t reaaaaaaaally urts when he says stuff liek that to me last night, and then the very next day he posts that on her wall?! he never posts that kind've stuff on my wall :/ like the most ive ever gotten where words arent involved is ''<3 :D '' whats going on? should i be worried? thank you for any responses :)!