18 and 2 babys?

So when I was 16 I got pregnant with my boyfriend of 2 years now. We had a baby boy (Now 5 1/2 months). We occasionally have sex once in awhile, we do use condoms, however I cannot afford to get on birth control ( my copay was about $100!) we are a little scared at the moment because I have not gotten my period this month. My last period was on September 23. Is it too early to take a test? I do not have any symptoms, I feel like I am going to get my period soon cause of cramps. What do you guys think?