Be careful about assuming too much. You say that you know "surefire" that your university is spying on you, but your only evidence is that your mom is computer illiterate and you're "sure some of them know more than they should" about you (WARNING - this is a red flag for those of us not in your situation, you do indeed sound extremely paranoid).
If you don't use the university network (which seems unusual when you're on campus with your computer, but I'll take it as given), then your university has no interest in your browsing history, full stop. If someone there in some way helped her get access to your activity, they could go to jail.
You wonder if your mom has conscripted your neighbors into her spying scheme (another red flag). Unless your neighbors are the absolute pinnacle of unscrupulous busybodies, they have no interest in your browsing history - they could also go to jail.
Very few people could legally help your mother to spy on you, and no one is interested in breaking the law to spy on you.
The ISP could theoretically provide her some of your browsing history:
- If they offer some sort of network monitoring service for child safety, then they would provide her whatever they offered to provide her, but it's highly unlikely that such a service actually keeps records, and more likely that it is meant to just block content - if you're not being blocked, such a system wouldn't care what you're doing.
- If you fall afoul of the DMCA by downloading copyrighted content and the copyright holder both discovers you and sends a notice to your ISP, that notice would be forwarded to your mother as the ISP account holder.
... ISPs are big, they have a lot of customers, and storing browsing history takes up a lot of space they for information they don't want to be legally liable for (e.g. if they record browsing history, they can be subpoena'd for it), so it's unlikely that they could provide this information to your mother.
That's assumption 1.
You then say that she knows what you browse whether you access it over HTTPS or not. This categorically rules out any sort of "from a distance" spying - once your request leaves your browser, no one knows what that request is until it reaches the server it's going to.
What this means practically is that if you use HTTPS URLs, someone (theoretically) could know that you went to YouTube, but they couldn't know what you watched. They could know you went to Wikipedia, but not which articles you read.
If someone is capable of breaking HTTPS encryption, that person has far more lucrative opportunities than helping mothers spy on their sons.
Even if you're mistaken and only HTTP URLs are affected, it still requires someone to basically perform an illegal wiretap to access that information because, as we've determined above, no one who has direct access to your browsing history is interested in keeping it or showing it to anyone.
Which leaves us with what is by far the most likely scenario:
There are oodles and oodles of spyware programs out there that have varying degrees of legitimacy - as others have said, many are marketed as tools to give parents just this level of access. Your mother could have found such a tool by typing full sentences into Google easily enough, and they're probably one-click installers just for people like her. Have you confirmed that there is no hardware device like a keylogger installed on your machine? All of these methods get at your history the moment it's created, before it has a chance to be encrypted or go over the wire. They are also the most legally defensible ways for someone to view your browsing history.
A big honorable mention goes to the person in the other answer or comment that suggested that if you have a browser profile logged in on a computer that your mother has at her house, then she can view your ongoing internet history as if it were her own. Simplest fix would be to browse in in-cognito mode (or equivalent for your browser if not Chrome), it won't record your history.
As for what to do about all of this, I'm going to go the tough love route:
- Talk to your mother. Tell her to back off, or if she won't tell her she's welcome to view your history but it won't change what you look at. You're a big boy, act like it.
- Pay for your own ISP. As I've stated I don't believe this avenue is being exploited to see your information, but if she's paying for your service and using that as a justification to spy on you, then it's time to take the next step to separate yourself from reliance on her.
- Reformat your computer. If there's any concern that something is installed that you can't find, just backup your important documents, erase the thing and start over. Don't put a bandaid on a bullet hole by using ways to hide your traffic from spyware.
- This one I'm just throwing out there to see if it sticks, if it doesn't describe your scenario then sorry, I'm mostly keying in on the above mentioned red flags: if you're off your meds, get back on them.