Your last period STARTED on December 30. Normally you will ovulate between days 11 and 16 of your cycle. Day 1 is when it starts. Sperm can survive UP TO about 5 days.
You had sex on Jan 10 - Day 11 of your cycle with your best friend.
You had sex on Jan 12 - Day 13 of your cycle with your ex boyfriend.
You had sex on Jan 14 and 19, days 15 and 20 with your crush.
If you are pregnant it could be either of them. The withdrawal method is not reliable.
Take a home pregnancy test. You MUST use your first morning urine, your wake up pee, for the best accuracy. If it reads negative, and still no period by about 10 days late, retest.