So I slept with one person on the 29th of April and with my boyfriend both before and after this date. Though I think my last period was around the 27th of 28th of April I had an ultrasound which gave my due date as the 31st of January and conception date of April the 27th. I am planning to get a dna test but wondered what the odds were..

Dating is merely Best Guess and as they are so close it's impossible to tell without a DNA test being done.

Thanks for your answer, when I asked the midwife about this she didn't explain it clearly but was talking about may the tenth which confused me even more