As they said, reset your router passwords, do a fresh install etc. All of this is very advisable, and I will not repeat what they wrote. What I will add is this:
Have you tried posting a similar question to an antivirus forum? Such as Avast, Avira, Macaffee, Bitdefender etc.? Some may only go indepth ii you are a subscriber, but in your case, I would recommend becoming a subscriber and installing the best antivir you can. Make sure you only use a reputable antivir. Others will know better which to use.
Also avoid computer-help websites that offer telephone service and cost money. They are huge!!!! scammers. See the youtube videos of it you want. There are hundreds of them, if not thousands.
You should also consider contacting your ISP, perhaps they can offer some assistance, by maybe putting up a strong filter for a limited time on your connection. This would restrict your internet use, but might be useful for the short term.
Additionally, make sure you ring up your bank in case you do online banking or use your credit/debit cards online, such as on ebay and amazon etc. They could put your accounts on higher alert and give you sms notification whenever an online payment etc. was done.
The tape on the webcam is also a useful suggestion until you sort things out.
Cheers.