Scared to death.....

So, I am almost 8 wks pregnant with my second child, my husband of almost a years' first child. We are crazy about each other and have been together since last May. We only dated for a little while and fell head over heels in love with each other when we spontaneously decided to get married ASAP. 
When I had my first baby doctors appointment last week, I found out that I now have chlamydia. I didn't have it in March of 2014 and he swears it didn't come from him, even though he's never been tested. He automatically blames me when I have been tested for fear of getting an STD. We have both been treated now but I am still terrified of the long term outcome of this since I'm pregnant. 
Why is it automatically my fault and he has no blame in any of this and why do I feel like we've lost a significant part of our trust in one and other???