Doxycycline - broke capsule and think I have vision problems

Hi, I started taking 100mg tablets (1 per day), 3 days ago. However I've had to stop because I am very worried about a couple of things, mostly my vision which I feel has been affected by this anti-biotic. Basically I can't swallow pills or capsules, so on the first day I emptied some of the capsule into a glass of coca cola..about 1/3 of a capsule at most. I did it several times throughout the day. In total I have consumed around 2.5 to 3 capsule's worth. I've stopped taking Doxycycline altogether, yesterday. Why? I feel terrible, it's like I am on some kind of trip and my vision is blurred. Things aren't 'registering' when I look at them, if you get what I mean, like they normally do. Have I done some damage by taking the drug like this, or have I had only a temporary, adverse reaction? I'm a bit worried and I know it was a stupid thing to do. I am convinced my mental state and vision problems are down to this drug. Thanks for any advice you can offer.