I desperately want to get out of slump

I am not able to overcome my slump. I don't know what I have been doing for the past one year.first year of my PhD was great. Wrote a paper(which got published), attended prestigious conferences in my field. 2nd year just wasted away in anxiety and self doubt. Finished one paper from first years drafts somehow and submitted it.still waiting for a response from the journal.

My self confidence has shattered so much that I have spoken very low of myself in front of my PhD supervisor several times, so much so that I am afraid they are not happy with me.

I have been a good student in my grad and post grad days. I have been appreciated by my supervisor a lot in my initial days, and I want to gain back the confidence. But I am not able to study more than an hour or two.

Now I am in my third year, and my data collection has just begun. And having wasted my 2nd year I feel so overwhelmed that I almost cry every time I make up my mind to study.

Is there any piece of advice I could use ?