Saw a old picture of my bf and his ex is it normal to feel like this?

[Bella]

So this girl he used to date (im friends with her and I like her and she has a bf too) but I was looking through her Facebook profile pictures and I saw a old one (last year) of him and her standing in front of a river or something. I was actually about to stop looking hoping it wouldnt come up but it did. Right when I saw this I exited right away didnt even see the whole picture and my heart dropped and I panicked for a second. Now im holding back tears and I look like I just saw a ghost. Me and him have been dating for 5 months and I was just wondering if it is normal to have reacted like that? I was really freaking out for a second and it felt like my heart poucned out of my chest and thinking about it I swear I heard it beat really hard . Is this normal? How do I not feel like this cause I'm sitting here feeling like I'm in shock! My heart feels closed and my eyes are wide and I could taste the shock in my mouth literally its like I could feel it when I breath! (No jokes) help?