This is urgent! please tell me if my computer has a virus?

well yesterday i went on this website a few people recommended to me, to watch episodes of programmes, and it came up with them 'you have to take this survey' thing first. i clicked on it etc etc. then i just shut down the whole thing because it sort of froze my computer a little. after that i've had a few security warnings and things like your computer is under danger and everything, and all these security stuff. i don't have security on my computer and random things do sometimes come up anyway. it says i have to pay for it but i don't want to incase it's a con. is this a virus?