Your assumption is probably flawed cause:
a) Your IP address (specifically, the external/public one), changes every time you change from one internet connection (like a coffee shop wifi) to another (your home), and that IP, commonly represents the entire network of computers connected to the coffee shop. And as a note, knowing someone’s IP address, is simple, and normally is not a security risk. (There are exceptions)
b) Knowing that, viruses and trojans are very common, but specifically targeted spyware (Spy software targeted at a specific person), are not.
If you still suspect being targeted by a hacker, or being spied with malicious software, I would suggest:
a) Consider formatting your computer
b) Use a Antivirus solution, and do scans often. (Check AVTest for insight on which av you should choose)
c) Keep your computer, programs and others UPDATED, this is very important.
d) Watch out for phishing emails. (This means, seemingly legitimate emails trying to fool you into giving login credentials, or downloading malicious software)
e) Don’t use public Wi-Fi networks, hackers can use public hotspots to tap into internet requests, in order to spy on traffic, or even get passwords. (History)
PD: Can you please tell me, what have you noticed on your PC that makes you believe you are being spied? Be more specific.