I see my own former situation in your cycle,Zygara, and I'm very convinced by your descriptions that it's time to get serious about qualified therapy...not just a counselor, not just CBT therapy. Deeper therapy will bring out the infatuation relationship that develops between therapist and patient where it can be helped in a healing way instead of just haphazard. All of this is very much relating to Transference issues, if you're familiar with that term. We talk about it a lot on the forum and you can look Transference up on the web to learn more about it if you don't already know. You didn't mention it in your post, although you described it in words like infatuation and depression that soon follows.
See if you can find a therapist trained in Relationship Therapy as those are especially experienced in attachment issues. It would be so great to reach the deep issues you're struggling with, as these kind of problems go on into adult life and affect marriage, job, and everything else. I think that it would be especially important to start now, as you're already in despair over the long dry summer and self-harm thoughts. There is a lot that can be done for you, believe me, as I see a lot of myself in your description, before I worked with my present T. Therapy can be hard work, but it's way better than suffering from extreme swings, or being alone with it, or unbearably bored year after year.
If I were you, with all the experience I've had, I would call that new therapist and tell him how down you feel and thoughts to self harm. And if he doesn't schedule you in next week, go to your county health clinic and tell them. I just couldn't sit around all summer feeling so bad and waiting for someone to do something.