Can I still get pregnant if condom slipped off after ejaculation but still on tip?

Yes, absolutely. It sounds like you were also starting your fertile time of the month, too. That would make pregnancy more likely. You can get pregnant from sex you have up to a week before ovulation.

If you're going to use emergency contraception, I suggest Ella, as it's more likely to help if you're fertile. You have up to 5 days/120 hours after sex to use Ella. It's more likely to help the sooner you take it. You should be able to get it from wherever you can usually get Plan B.

Emergency contraception is not as reliable as regular hormonal birth control. It's simply worth a try in the event of an emergency.

It's worth doing an internet search on correct condom use. There are things you can do to prevent the condom slipping like this.
Never continue sex once he's ejaculated.
Never continue sex once he's started to lose his erection.
He should always hold the base of the condom on his penis as he withdraws from you.