Concerns about my mental health

Recently I feel like my mental health has been slightly declining. I've noticed that recently i've started thinking negatively of myself again & also randomly get really sad for no reason. The negative thoughts of myself concerned me when I began thinking that i'd be better off dead because my life is meaningless & i'll never amount to anything, so what's the point. I also thought i'd be doing myself/people around me a favor by simply ending it. I don't believe i'll act on these thoughts. I also haven't told anyone about this & have been debating as to whether I should let my therapist know this has happened. I'm on anti depressants & feel like they don't really help. Should I consult with my doctor about my medication? & What do these thoughts mean? I don't want to use the term suicidal, but I don't know if that's what I might be? Apologies for rambling on for so long, I know this was a long one, though, thank you for taking the time to read this.