Conception date help!?

April

So my last period was Dec 20-25th. My first period since I've been exclusively BF my 8 month old. Anyways I took a test around Jan 19-22th it was negative. Took one the 27th and it was a vfl but taken 9 and they just kept getting darker. So just wondering if anyone could help with maybe around the time I would of concieved? My first baby doc U/S app is the 28th but I feel like it's taking forever waiting to know anything besides I'm pregnant. 🙂 Thank you lady's! 🙂