What are the chances of pregnancy if condoms were used but he didn't pull out?

No Leakage, no worry. If the condom functioned as it was supposed to, there is no worry. If any semen entered your vagina that is a different story, but as stated, you should be fine.
Possible. If condoms are used perfectly, the chances of pregnancy are low, but condoms sometimes break, fall off, or are put on too late. So condoms are not 100% effective in preventing pregnancy.