Traumatic Dreams

Hey ladies, I just found out Thursday that I'm pregnant (5 weeks, 1 day) and it was completely unexpected. In fact, it was right after I told my husband that I decided I didn't want to start trying for children (if at all) for another 2 years since I just quit my full time job to start a business with two partners as well as become fitness instructor. I'm terrified and feel like a terrible person. Everyone out there is posting such happiness and excitement and I'm just filled with fear, terror, and to be honest, dread. 
Financially, I have no idea how this will work as our budget is already super tight. I don't have family near by so support from family will be far and fleeting (emotionally they'll be there, but it'll just be me and my husband). I've started having nightmares where I'm waking up gasping for air to breathe and sobbing. I get it, there is an adjustment period and I'm definitely in it. And we do want kids, one day, just not now. But here we are. 
I think the part that has me so shaken and upset above everything else is this. My sister, who is my best friend, has been trying to conceive for 5+ years now and she has been heartbroken and depressed over her journey, and I have no idea how I'm going to tell her. I know this entire pregnancy I will feel guilt and sadness at each milestone because of how I know that even though she will ultimately be happy for me and love me, it will quietly break her heart and keep her in tears.