Yes, I agree with everyone, you MUST tell your psychiatrist or psychologist. This stuff's not to be trifled with, which I guess you know, as you're asking about it. It may well be that you need a meds adjustment, or maybe you need to talk through things with your T about self esteem and hope issues, and is there something underpinning these thoughts?

I had, I guess, the opposite problem, I was all too aware of how profoundly suicidally depressed I was (had lost everything to Bipolar and long-term mis-medicating by psychiatrists). I told my psychiatrist at the time, every single time I saw him how depressed I was and he didn't act to help me. I made a 100% serious attempt on my life and was in a coma for 5 days and only survived because of an amazing sequence of events and the help of Police, Ambulance, ICU etc. I mention this as a cautionary tale. If you're aware that some type of trigger even somehow relating to suicidal thoughts is happening, get help from your mental health care team and don't stop until they help you. They are not always as responsive as they should be.