You all are very young. The vast majority of relationships at this age are transitory. Being away from each other may give one or the other people involved some freedom they didn't realize they craved, and being reminded that it is only temporary may cause resentment, which would explain the constant bickering. OR, one person or the other may be insecure about their BF/GF traveling around without them, and may picks arguments because of that.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?