Is it normal for me to think of my daughters father (ex-boyfriend)

My story starts 2 years ago i met this guy and dated him.In about a month i found out i was pregnant not knowing what to do because he wanted to get married i decided to move to a diffrent city lying to him telling him the baby was not his.When i was 6 months pregnant i decided to call him and tell him the truth that i had made a mistake, by that time he did not believe me and denied baby was his.I later found out that he was in a relationship and had got married.
Since then i decided to forget he existed and i never called him again i had my daughter amy and when she was 2 mos i met this person who said he was interested in having a family with me with my daughter he told me,"just preted that im the one who got you pregnant and we will tell her im the father.
Now amy is 1 yr and 3 mos and her real father is back in our lifes he is still married and a dna test prove his paternity of my daughter. now he want to be in her life. My problem is that my boyfriend doesnt want that to happen he is to controling and jealous. its wrong because my daughter is first amy has the right to know her real father.now im having problems in my one year relationship and the biggest problem is that i cant stop thinking of my ex boyfriend amys father. is it normal i am always thinking of him i cant get him off my mind. he calls frequently but we never talk that long by what he told me last time he said he wanted another chance to be a family i think he still has feeling for me his sister told me he even dreams of me. is it possible all i know is that i do love him but he doesnt know and i dont know what he feels for me. and i want to end my current relationship the thing is that he is married. its not possible. i want the best for my daughter and me and that to be with her dad. im confused could it be that i just want what i cant have?