Periods

I breastfed for about a month and a half after my little bitty was born, he got so sick from it I had to stop :( anyways I had my last period the 8th of August and my baby on the 23rd of June...I haven't been exactly safe, I'm not on birth control and no condoms. My husband and I have a very active sex life...he just refuses to wear condoms :/ anyways, I tested last week and it was negative. What's the chance of me being pregnant again, or are your periods just completely screwy after haveing a baby? Thanks.