I understand your worry.
You can rule out pregnancy
by doing a simple home urine pregnancy test. The kit is available over the counter.
I am sorry that you suffered pre-eclampsia before.
There are two options for contraception
You can take a regular birth control pill like femilon
but since you had pre-eclampsia before, you need to confirm with your doctor if you are the ideal candidate for it.
Another option is you can go in for Intra uterine contraceptive device (IUCD) like Copper T. It acts for a minimum of 3 years.
Some of the oral contraceptive pills
are available over the counter.
Hope this helps you.