New girl v ex

[springboard]

I've started seeing a girl that I met on holidays over Christmas.Its a long distance thing,but we've met up a few times already and talk alot on the phone.I've really fallen for her and want it to work.However,I bumped into my ex who lives near me and still have really strong feelings for her.We had a stormy relationship as I was going through alot of problems at the time.I let her down alot and wasn't very good to her but we remained friends until recently and I miss that.But I also miss the sex and get really turned on just thinking about her.I have also been making excuses to contact her and denied that I'm with someone else.Is this wrong and will it pass as the new relationship develops?