Doxycycline Monohydrate and lyme disease

I feel like I am SO tired on doxycycline. I'm on it for Lyme disease, had Rx for 3 weeks, was off it a week and started to have the joint pain relapse, so now I'm on it for four.
It seemed that I was finding myself with very shallow breathing too. It seems if I forget to take a dose or two, I'm not as tired.
I'm less focused and more forgetful, it's hard to get things done.

I see that of only 2 postings as of this one from me, one mentions feeling "generalized weakness and fatigue." BINGO! Me too. And...like the posting I'm referring to, the patient is taking it for Lyme Disease. I know that, itself, can also cause weakness and fatigue. But I too suspect the Doxycycline is contributing to this in my case.

I am being treated for lyme disease with 400mgs/day. I take 200mgs in the am and 200mgs in pm. The course of treatment is for 4wks. I am in my 2nd week. I feel just awful. My side effects are nausea, generalized weakness, fatigue, abdominal pain, headaches, joint pain and stiffness. I did not have these symptoms (except joint pain) till I started the meds. I feel worse now than before I started this medication.