On jan 29 I had unprotected sex a one night stand .. I remember that on feb 9 th I had a period I don't remember if it was the beginning the middle or the end I just know I had a period that day and I don't remember if it was normal.. Then in feb 23 24 and 28 I had unprotected with my current partner .... In march 11 th I found out I was pregnant ... My question is , can there be a chance that the baby is from the jan 29 guy ... ??? On march 22 I was 6w 1d by LMP but measured 5w 2d by US WITH no yolk or fetal pole seen per the doc notes .. And on April 8th I was by LMP 8w4d presumptive (what ever that means )and by US 7w 5d so with these being my first ultrasound is there any way my pregnancy be the jan 29 guy ???
If you had a period on Feb 9th it it unlikely you were pregnant. Having sex on Jan 29 it may have been too late in your cycle for you to conceive, if the Feb 9 was the beginning of your cycle. If it was near the middle to end of your cycle the odds favor you NOT getting pregnant then.
The 23, 24, and 25th would be likely right around your peak fertility. There is a good chance you got pregnant then.
The dates favor the end of February. Do NOT look to deeply into the dates. They are NOT exact. Nobody, not even your doctor or an ultrasound can tell you exactly when you conceived. They are all approximations. Most doctors base dates on your LMP. Why? Because almost all women know exactly when that was. 8w4d prior to April 8 was February 7 - close (presumptive).
The approximations would not be off by almost a month. A week maybe but not much more than that.
It is unlikely, very unlikely, the Jan 29 guy is the father. You can confirm paternity with a DNA test but I don't think it necessary.
Good luck, hope it helps.