I was the exact same when i switched from treadmill to outside felt like i was starting all over again but don't worry it will get easier soon!!
I kind of hit a stopping point between wk 5/6 and my holidays i couldn't seem to reach the 20min run. I joined a running club a couple of weeks ago and things have gotten better as have done a couple of 5k runs with people in the same boat as myself. I'm still finding the running a struggle and am very slow but it defnitley seems to get that little bit better everytime.
if you can find someone to jog with you it makes such a difference as you can encourage each other to keep going!
Keep up the training and make yourself a good playlist and you will get there