5 months you cannot count a month as just 4 weeks then women would be pregnant for 10 months a month is usually 4 weeks and at least 3 days so hopefully that helps
Your 4months at 16weeks, so your 4months and 2weeks in your 2nd Trimester
7 days in a week and on average 30 days in a month. Take 7 x 18 = 126 then divide by 30 = about 4.2 months to be exact
You're in the first week of your 5th month.