Losing feelings within 2 months?

Gf and I (M&F) are in our early 20's, and have been together for a year. I had to go on a trip abroad for 2 months, and we were both lovey-dovey before I left and things were perfect. We texted every day and spoke on the phone 3 times. Everything was fine till maybe half-way through the trip, she slowly stopped texting me in the mornings, speaking less, and becoming more distant etc.

I came back and we talked, and she said due to the distance she wasn't sure how she felt about me anymore. Then a week later we took a break for her to find what she really wants- that's supposed to last 3 months. I just don't know how everything's so perfect for a year and somebody loses feelings in just a couple of weeks like that. Is that normal? Why do I get a feeling she's not coming back after the 3 months. Oh, she also got the implant birth control not long after I left, could that have had an impact? Her libido also dropped at the same time too. I just feel so broken inside I've never met anyone that made me feel like this for her. Any help would be appreciated.

tl;dr: Together for a year, I went on a trip for 2 months, came back to find everything in pieces. Is this normal? Possible effects from getting the implant?