Trouble with running

Hey fellow runners!

For the past few months, I've been having problems with running. I started running consistently 1 year and 4 months ago, and when I look at my stats, I was running way better 1 year ago than I am today, even tough, I have structured plan now (such as intervals, tempo runs, long run, recovery run). 1 year ago when I went out, I ran 5km without stopping in 27minutes, but today, I can barely run 5km without stopping and I run it in around 31 minutes. I don't know what the problem is, I can barely hold the pace 6:00min/km for a few kilometres and then my mind just switches off and my legs can't work anymore. I make sure, I eat properly, sleep alot (8-9hours every day) and have rest days.

I feel like I'm shit with running, I constantly need breaks when running. I love running but I hate the feeling that I always need to stop and catch a breath. I also want to improve my speed but I just can't seem to get there.

Is it normal to have such periods with "off" running?

Thank you all in advance for your advice:)