Is it possible to get pregnant during the 22nd-28th day if using a 21 day contraceptive pill?

Unlikely: Very unlikely. While no day in one's cycle is 100% 'safe' it's very unlikely on the days that you describe.... Especially if you haven't missed any pills. The chances of pregnancy when one uses the pill perfectly over the course of 1 year is around 4% or 4 out of 100 women will become pregnant on the pill using it perfectly. If you're worried, can always use a 2nd method like condom. Best luck.