How can it be that someone is constantly in my computer, every day something is changed

Microsoft is unable to determine who is in my computer changing icons and or sounds, removing documents etc. I am so tired of calling them, every time I run a scan threats are removed, how can I stop these bastards. They overtook my face book and phone, they deleted my contacts on my phone and made their own, then when I went to ATT they said since my phone was made Internationally it could do anything, when in fact my phone is made by a com,pany in florida, how is it that I block people on facebook and google but somehow they befriend themselves and are able to send messages to me? When I complain of these things to my family they think I have detmentia, this all started the night Al-qaeda and Boko Haram bombed in Afghanistan and in North Africia and two people whom I was chatting too asked for money to be sent to Paris, sure enough the next day Paris was attacked. I have never befriened someone in the middle east, but yet I get private messages, from Iraq, Afghanistan, Nigeria, countries which I believe are block from OFAC.   Today I am unable to access my google account as step two verification has been turned onl. back on the phones again, they will fix it but can never tell me why it happened. does any have any suggestions how I can check???