Adorable- I just read this thread for the first time and i think i understand what you are saying. (If Im off base then at least this is what I think)
In high school (at least mine) all our worries were what we were going to score on our chemistry and math regent. We were in our little cacoon of tests, shabbatons and play and never really understood what our teachers meant by internet is bad and certain places are bad. You knew that it will never affect you.
Now that you are out of school in the working world and single, there are no teachers guiding you and naturally you get pulled by certain attractions that you never knew existed. Especially now that there are more worries (shidduchim, work issues….) Its nice to find other means to make you happy, so you turn to other things. (email, websites..) Even on kosher sites there can be innapropriate things! Now you feel that your not that sweet aidel BY girl anymore.
You still are!! Just move on and the fact that you its bothering you is a good feeling. Im not sure what exactly is making you feel unpure but whatever it is you are obviously smarter not to go there again. Also try to attend speeches once in awhile or do something that makes you feel pure (i still keep my 12th grade chesed job and it makes me feel so good!)
B’hatzlacha!