Could my ex possibly be the father of my baby?

Patient: I would like to know an opinion of who my baby father might be.I had sex with my boyfriend on the 11th 12th and 13th of febuary.Then my period came on the 14th of febuary and ended on the 20th.On the 19th I had sex with my boyfriend.On the 21st unfortunately I had sex with my EX he pulled out to precum and went back in.On the 22nd and 23rd of Febuary I had sex with my boyfriend and that weekend.On the 28th I thought I saw a spot of pink blood but also the week my period ended i felt nausea.My boyfriend and I have been trying on and off for 3yrs.