It certainly sounds as though you have started doing all the right things!
Clearly your experiences are much the same as those of countless Christians over the centuries, and hopefully that will encourage you. You are neither unusual nor strange, but very human. Being human, you are fair game for Satan, as are we all. Trust in Jesus, He will get you to His heavenly kingdom. All you have to do is ask Him. When I find I am being distracted by wandering thoughts or voices when I am at prayer, I ask Jesus to back me up with His grace, and then I denounce Satan and order him to be gone, then return to my prayers. I sincerely hope it upsets the devil(!) but it doesn't stop him coming back for more of the same. He's a very slow learner, but refuses to give up easily. I comfort myself with the knowledge that my team (well, Jesus' team actually) will always prevail.
This trust in Jesus is also relevant to our unworthiness and sinfulness. As long as we keep asking Him, He will forgive us and accept our frailties. He will never let us down, all we need to do is accept that He has everything under control, and we can trust Him implicitly.
I suppose this sounds rather simplistic, and there are those who would seek to complicate things, but in reality Jesus' Way is very simple - even if it is difficult. I subscribe to the concept of keeping it that way.
I hope this helps,
With love and prayers,