Help me i lv the rong girl?

i hv a gf hu i have been dating 4 ova a year now and i always fout i loved her at the strt fings were gr8 bt ova the past 4 months my ex keeps on popping into my head and i get all nervous n awkward round her ive admitted i like her n she likes me she offered to play wiv me the other day n i dno wt 2 do cs i really like her and i dnt like my gf anymore. but im in 2 deep wif the gf her dad ant the bloke to mess wiv n ive had 15 guys warn me if i hurt her im dead. i no im doin rong but i cant help it everytime im wif my gf i think about the ex and im in love with her