I'm having the same issue. Except that I couldn't even get it in more than a few millimeters before it started stinging and getting it out was agony, I'm still sore 20 mins later!
I've tried them a few times in the last 2.5 years since DS was born and they've always been uncomfortable but never stung like this.
Was meant to go swimming tommorrow as part of a 6 week challenge and now can't go because I can't get the stupid tampon in. :'(