wifeywilson20, It is very unlikely that the IUD can still affect you now. If you menstruate regularly, the chances are very very good that you are also ovulating regularly.
There is only a 7 day window where sex can make you pregnant every cycle. Even if you do have sex during those days, there is only a 30% chance that you will get pregnant.
If you had unprotected sex Jan 30, the bleeding on Feb 3 does not have anything to do with pregnancy. Nothing can happen in 4 days. Even if the sperm met the egg immediately and managed to fertilize it, it was still floating down your fallopian tubes after 4 days.
It probably felt and smelled different because it was not a normal menstruation but bleeding.
If you used an early detection test kit, it should show positive by now. You can wait another week and test again to double check.
Are you trying to conceive?