Hi,
yes it is possible. My first symptom this time (that I really knew something was up) was that my blood sugars (I am diabetic) started acting really strange about 4 days after the IUI. Also was having bloating and feeling extremely tired starting about the same time.
I got my first BFP (very faint, but visible) on Day 10 after IUI. I am now 4 weeks and 1 day pregnant and hoping hoping hoping and praying this one will make it. Feels different this time compared to the ones I lost so I am very optimistic that this one will make it.
5 days is the earliest, once you start producing HCG symptoms are possible. I started throwing up 6 DPO and heartburn at 8 DPO, BFP at 13, good luck :)
It's possible to have implantation as soon as the embryo has hatched, but that is at least 5 days from conception. You wouldn't have pregnancy symptoms until at least implantation, and probably not that fast even so.