Swollen eye help please?!

I was on a retreat with my youth group this weekend and Friday night I noticed my eye was watering a lot. I thought it was because I was getting sick, and woke up Saturday with a full fledged cold and my left eye was kind of swollen and red. It continued to water throughout the day, it kind of looked like I was crying. Also it continued to swell and was red. There was no pus in it and it didn't itch or hurt, it's just watery and swollen. I took an allergy pill last night, which didn't help at all. This morning we were up and leaving at 5:30am and my eye was about the same maybe a little worse. I took some Benadryl and slept in the van for about 3 hours. When I woke up the eye was less read and the swelling had gone down a small bit. Anyway, I slept the rest of the way home (3 more hours) and my eye is still swollen. What's wrong with it? It has no pus, so it can' be pink eye. I am allergic to cats and dogs, but I wasn't around any this weekend. Any ideas of what's wrong and how I can fix it?