i tried to have sex (using double condoms which didn't break), but we had to stop

First of all you should never use doubled up condoms as they can slip off easier, the light bleeding a week after taking the pill is normal, what you will probably find is your next period will be later than it normal is and will take several months to get back to normal again but you have no need to worry at all.

thank you very much.

Next time you try to make things easier first have lots of foreplay so your vagina gets relaxed and ready as it needs to expand ready to accept the penis and without foreplay that won't happen, remember only use one condom and extra water based lubricant on the condom, around the vagina entrance and inside and lastly try to stay relaxed as the penis starts to enter or the vagina entrance muscles will constrict and make it painful and almost impossible for the penis to enter.
If you have any more questions feel free to ask :)