Bike tire question for 280lb(124kg) person?

[AryxasofLore]

Hi. I am 19 years old and weigh approximately 280 lbs. I have recently started biking to work (30 min hard ride) to lose weight, and was looking for tires to support the trip.

I bought the bike for $400( CCM full suspension bike) here is an image to a similar bike(
https://www.google.ca/search?q=ccm+presto+700c+road+bike&bav=on.2,or.r_c p.r_qf.&bvm=bv.47380653,d.cGE&biw=1517&bih=714&um= 1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=ftWuUcK7 OeHeiALsy4C4Bw#um=1&hl=en&tbm=isch&sa=1&q=ccm+26+m ountain+bike&oq=ccm+26+mountain+bike&gs_l=img.3... 12808.16129.9.16260.11.11.0.0.0.0.113.1082.7j4.11. 0...0.0.0..1c.1.15.img.RY3y3c_rwhc&bav=on.2,or.r_c p.r_qf.&bvm=bv.47380653,d.cGE&fp=819b3af44ec809cc& biw=1517&bih=714&facrc=_&imgrc=Hkxn_GEDA9UaZM%3A%3 BOUAJy5JqH1-8vM%3Bhttp%253A%252F%252Fwww.onlineauctioneer.ca%2 52Fuploaded%252Fimg%252F571__Picture%252520016.jpg %3Bhttp%253A%252F%252Fwww.onlineauctioneer.ca%252F offer%252Fdetails%252FCCM_Static_26_(10-094)-571%3B1200%3B900

I noticed however that when I sit on the seat, my back wheel( thought not completely flat) flattens out, and when I hit a bump in the road, the rim ALMOST hits the ground. Now, the frame is perfect for my size, and is VERY STURDY, but I seem to be having problems with the back wheel. It pierces VERY easily, and since this is not the first time it happens, not the first bike it happens to, I am starting to think it has something to do with my weight. I am not Obese, just muscular and chubby, but I was wondering if there are some tires I can use that will take my weight without going flat or getting pierced easily? I have seen bigger people over 300 lbs using road bikes with their tires fully inflated with no problem.

So here is my question: What should I do to keep my wheels from piercing and what kind of tires/tubes should I look into buying. I do not want to spend more than $150 if possible, as I need to save up for university.

I NEED to lose weight, and riding my bike is something I have loved to do since before I got injured and gained weight. I want to get back into shape so I can get back to trail blazing with my bike in the mountains.

just once more, what kind of tires should I buy, or if I do not need tires, how much pressure should I put in the wheels to keep them from flattening out when I get on?
where I live, there are potholes and the roads are smooth, but there are the occasional rough patches on my path
26" rims

[HoldenMcGroin]

If you ride on pavement get some semi-slicks (26×1.50 to 1.95). Replace the thin rubber rim strips with plastic rim tape, its thicker and provides better tube protection. Inflate the tires to the stated max pressure on the tire's sidewall.