Am I the only one that goes 20mi/h?

I’m 39. I came to the UK 4 years ago and got my driving license 1 month ago but started driving this week.

As the insurance was so expensive for me, I chose the “black box” discounted plan. The box will be installed in the next weeks.

I need to be very careful with my driving because I don’t want to lose my precious license, so I’m stick to the law but I feel that I’m the only one doing it. Everybody goes 30mi/h in a 20mi/h zone and only reduce their speed at the cameras.

I feel I will cause an accident as everybody is overtaking me the whole time.

Any suggestions? Thanks in advance!

PS: I’ve driven for almost 20years, but in another country, in the other side of the road.

UPDATE: Thank you everyone for your comments. You have added a lot of perspective to my doubts.