Missing my ex??

2 years ago i got with my best guy friend but after a while we broke up and then when we agreed to be just friends we drifted apart and didn't talk for 10 months then one day out of the blue he texted me and we met up a few months ago for the first time in 3 years and ever since we've been keeping with each other off and on today he called me out of nowhere just to ask how i was doing and stuff and I don't know why but i got butterflies. i don't know if it's just my period hormones or i'm lonely or if i actually do kinda like him again. i mean he was my first love and all and i will never fall totally out of love with him but i just didn't think i'd actually get butterflies like i did when i was with him. it's weird and kinda scaring me.