Depends whatkind of wax you used?
If it was hot wax, itmight have been too hot..
whichever wax, you may have pulled the strips at the wrong angle or too slowly both of which cause a "tearing" effect rather than a quick pull and this causes the hair follicles to become red and inflammed.
If you had let the hairgrow long, it can sometimes cause the same problems- best not let it get toooooo long! LOL.
My other advice would be to have a warm bath before hand as it opens the follicles and makes the hair coming out let traumatic for the skin. Also, get some soothing after-shaving lotion which will help control the redness.
Slightly off subject- i used to wax but found it too fidly, time consuming and hated having to let the growth getlong enough. About 2 years ago i tried an epilator for the first time in about 20 years and was really impressed. I am a total convert! You can get rid of shorter hairs than waxing so you dont have the same regrowth problem. Its quick, clean, no mess and not fiddly- same motion as shaving really, and if you do it regularly not only does it become less uncomfortable (it has always been less painful than waxing for me), but the hairs grow back slower and thinner.
Worth giving it a try, but agin, dont let hairs get too long, hot bath first, and maybe take a painkiller an hour before. (also a good idea with waxing!). WOuld recommend an epilator with a little light on, helps spot the little fine hairs..
Good luck!