Frustrated with myself and advice needed for a newbie!

So hubby and I have just started ttc beginning of February. I went to my ob for my annual and we were given the go ahead and some prenatals to start adjusting my body for baby... Well obviously we have been BDing when we want and we have said from the beginning we wouldn't stress. Well, my sister and her fiancé just found out they are pregnant Sunday. I had been told that they weren't planning and weren't even trying for a baby... I was a little heart broken just because I then found out her fiancé had in fact wanted to get her pregnant. I guess I just need some support or advice as to how I am feeling. Of course AF showed her ugly face the very next day so that didn't help at all with my emotions... I know that we can keep BDing and maybe next month we could get a BFP but I can't help but feel discouraged and I don't know why... I guess this is more of a rant because I feel like if it doesn't happen next month, I will feel anger towards my sister!