Doxycycline Monohydrate side effects

Don't know if it's because of this medication but after taking it twice a day, after only 3 days, I had the most severe headache I have ever had. I couldn't even walk without it hurting. The was followed with me throwing up and this continued right through the evening. When I woke up the next morning the pain was only 25% of what it was the night before and no more vomiting. The next 5 days involved minor headaches that sometimes feel they're on their way to the same severe migraine I first had. Not sure if this is the Doxycycline Mono 50MG but I never had these headaches before and was wondering if anyone can relate to this.

I've only taken 1 dosage about 5 hours ago for a infected cat bite and I feel soooooooooooooooooo tired. I believe that the tiredness is directly related to the medicine.

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.

I have drank alcohol on doxycycline and have only had worse hangovers. I laid down once and my acid reflux acted up pretty bad.