I like to know both weeks and months just for me. So what I like to do is divide how many weeks I am by 4 and I know how many months I am.
This is the chart I use. Most count it by every 4 weeks which makes your 10 months even some doctors count it by this. Either way you're pregnant for 40 weeks. I like to use this chart which I google imaged pregnancy weeks to month chart and saved a photo to my phone. I use this chart because most doctors use it and it makes me feel like I'm not pregnant as long hahah.
First Trimester
1-4 weeks= 1 month
5-8 weeks= 2 months
9-13 weeks= 3 months
Second Trimester
14-17 weeks= 4 months
18-21 weeks= 5 months
22-26 weeks= 6 months
Third Trimester
27-30 weeks= 7 months
31-35 weeks= 8 months
36-40 weeks= 9 months
This is how a lot count it but again you can just count every 4 weeks but that would make every month 28 days and we all know that is not true only February has that many days(every 4 years). But again you're pregnant for 40 weeks either way.