<human>: Could you distill the essence of the text into 1-3 sentences?

I'm sorry to complain. I'm aware that compared to some people's problems, mine seem small but I'm not sure who to talk to and I need some advice. 

My bf and I have been together 4 years (since we were 15). He was my first boyfriend and we have always been very secure. I feel like I can trust him anything and I'm sure he feels the same about me. I used to see him at least 3 or 4 times and a week and we would text every day. In short, we are really close. 

In September last year he left to go to uni. We had talked about the fact that he was going and the fact I was staying home and we agreed we cared about each other too much to break up (despite the long distance) and that we would make it work. I didn't see him for 8 weeks at a time, and the times he was back were very limited as half the time was spent studying and the other spent with family. 

Now the first year is over and he's back, he thinks that surviving this year means things will be okay for the next 2 years, but in all honesty the last year has been hell for me. I missed him every day and I realised that without him around I had very little to smile about. I cried on a daily basis and became so unconfident at times, I was scared to leave my house. (Other things in my life weren't going to plan either and so it would be wrong to say his leaving was the sole cause of my downfall, but it was definitely a large factor.) 

Now his back I've noticed the change in me straight away. I'm much more confident and happier and feel so much more secure, but I can't stop thinking about the fact that in September, I'm going to go through the exact same thing all over again. Other factors in my life have been sorted out but I'm scared the same bleak feeling will come back. I love him very much and how I felt is in no way his fault but, is it wrong that he has such an effect on me? And how am I meant to overcome these feelings?
<bot>: While my boyfriend was at uni, I was overtaken by (undiagnosed) depression and the only thing which made me smile was him coming back. How do I survive the next time he leaves?