I'd recommend you to change the structure to the following:
Once I loved then I lost
loosing myself as a cost
thought to never love again
there you came running in
suddenly it came back
that beautiful feeling that I did lack
falling hard I was caught
even though I was already taught
taught of the famous lies
the I love you the despise
now I find once again
that forbiden love is about to win
wishing that you could see
what this is doing to me
I know this feeling deep within
make me fall in love all over again

This would give your poem a specific structure and make reading it easier. Futhermore it presents your poem better than a „wall of text“. That rather seems to scare people off. This is just a little hint to keep in mind that you have to capitalize the „I“. I don't mean to be a smartass, sorry.

The rhyme was nice and the flow aswell, though it got interrupted in between, but that wasn't too bad. Try to keep about the same amount of syllables in each verse, like that it'll flow really nice.

Okay now to the substance: I can feel the story you're telling, it's quite nice and touching. The way you started gives the reader a hint of your current situation.
"Once i loved then i lost
loosing myself as a cost"
I'm sure everybody has experienced this before, yet you shouldn't give up. Neither did the person in your poem. I have to admit that i like this part most though:
"falling hard i was caught
even though i was already taught
taught of the famous lies
the i love you the despise "
It got to me, though one should never give up in love. All in all i enjoyed reading your heartfelt poem and the emotion in it. Thanks for sharing and keep up writing! :)

* 'wall of text'
** 'I'

Jennis Comment Said It All.
Good Job!