Sometimes, the more you fight those scary thoughts, the more they seem to want to take over. Think about this- if someone tells you *not* to think of pink elephants, what is the very first thing you are going to think of? Of course! Pink Elephants! You seemed to indicate you started to do OK with your therapist and the support- then you slipped- Why? From my own experience, I think I know.
Instead of fighting your thoughts, and labeling them as either "good" or "bad" why don't you just observe and accept them? Yes, thinking of harming yourself can be frightening, but a thought is *just that* a THOUGHT- a thought alone doesn't harm anyone. Only actions harm. And you have a choice in that.
Why don't you try what I call "urge surfing"? This works splendidly for a lot of folks, and it may for you as well. Make sure you are in a safe, secure, quiet place to do this. Sit comfortably in a chair and close your eyes when you are having these thoughts of self-harm and suicide. As you sit with your eyes closed, concentrate on observing your urges (a.k.a. thoughts)- do NOT judge them- just observe them. They will grow, and they will lessen. Just feel them come and go. They will go up and down for a long time- probably for several minutes to an hour or more, depending on how long you have had them, and your level of coping skills. As you observe them, you will start to relax. This is a lot like meditation- it relaxes the mind and body, and those thoughts that were so frightening are suddenly put into different context- one that says- gee, this isn't so bad, what was I so upset about? As they become less and less frightening to you, I will predict that they will either disappear altogether or become manageable to the point where you can overcome them with the help of your support system.
It is your own *fear* and *obsession* with them that gives them power over you. As you accept them, your fear lessens, and their power over you does, too.
Does this makes sense to you?
That is not to say, sadly, you will never have another suicidal thought as long as you live. If you are prone to depression, it may of course be at least in part genetic , and you may of course have episodes in the future for which medications will need to be tried. But there are techniques that you can utilize where self harm and suicide will be fleeting thoughts here and there and not obsessive and constant when you are episodic.
Take it from me, I have suffered from mental illness from the time I could breath. Depressions were present since I was born. Then when I was 18 I started getting happier. Or so I thought. The "happiness" turned out to be the start of manic episodes. I had developed Bipolar Disorder. *sigh*.
I hope I was not intrusive and that I helped you. If I was out of line, just ignore me. However, most people who know me in person say for some reason I actually do help. Who knows why?