http://www.baby2see.com/pregnancylength.html
This has helped me a lot! You can specify it to view how many months you are. Next Thursday I'll be 26 weeks(6 months). It's confusing to figure by yourself though as you'll see. I keep a screen shot of mine personalized to help me know.
Every 4 weeks is a month
4=1
8=2
12=3
16=4
20=5
24=6
AND SO on hope helps