Due date question

My LMP was Dec 27. According to glow, I ovulated around the 15th. However, I started getting very light positives on Jan 30. I'm thinking I ovulated later. Do I still go by my LMP? The app says 3 weeks, 5 days. But every calculator I use adds 2 weeks. I know my doctor is going to go by LMP so I guess I'll wait until my first ultrasound.