Similar experience to myself many years ago. Looking back in the log book it shows for the fifth lesson (a previous lesson was two hours) 10A/10B. Like the OP I was feeling overloaded and although performing recovery, with and without power, quite well I realised then it may be a bit too early in my training. After talking with the Chief Instructor I took a break, changed schools and progressed at a more comfortable (for me) pace.