Girlfriend wont reply to my texts?

I'm a really clingy person, and I am fully aware of that. Apparently, my girlfriend thinks it's 'cute' but I know it bugs her.

Just recently our conversations have died down a lot, and holding a conversation for long is difficult because we either have very little to talk about, or I just get no reply.

It sucks because just recently she has been talking to more guys, even her ex's and people she previously liked. I'm just worried that she's been unfaithful in some way. It's a scary thought because although I trust her, it's been running through my mind like crazy for the past few weeks.

I've been dating her for a while now, almost 6 months, and just the thought of losing her makes me want to cry. She just never replies to my texts anywhere near as much as she used to, I'll get maybe 5 a day, tops. It's been this way for weeks.

We're in a long distance relationship, too. I know that makes a difference, but you'd think she'd be texting me more often because of this. It's not like she's busy, she's constantly updating her Facebook and BBM statuses, and she's talking to tons of other people. I just seem to be the last thing on her mind even though she's the first thing on mine.

It hurts to think that she's ignoring me. I'm sorry this is so long but I need answers and I need to vent. Thanks in advance :)