Well first its not a modem, its a gateway. I don't say that to be snotty, only to ask what you have plugged into it? Do you have a router too? If so that can cause problems.

Next, I would try to stay away from the CG3000d and atleast ask for the CG3000dv2 which has some of the bugs worked out.

Last, what are the signal levels. To find out fallow the instructions below.

1. On the computer that is connected to the gateway with an Ethernet cable, type http://192.168.0.1 in the address field of your Internet browser.

2. Log in with the user name admin and its default password of password.When you connect to the gateway the Gateway Status screen displays.

3. To view this screen, from Gateway Status screen, click the Connection Status button. See page 22 of manual for example.

Only have my PC connected no Router

Connection Status 

Connection

Ooh, those signal levels are REALLY bad. Im surprised the modem is even online. Here is a break down of what your signal levels should be.

Do you have alot of splitters between where the cable wire comes into the house and where it enters the modem/gateway? Do you live in a house or a apartment complex of some type. 

i am in a apartment complex and only 1 splitter from where it comes in

What kind of splitter? Try taking it off and making sure everything is tight then checking your signals again. If they only change by 4, then you need a technician. Might just want to call your landlord/sup and see who is responsible for what wiring in the complex.

Removed Splitter and now its 

Connection

Even after removing the splitter it happened again

It made your signal better then it should have though. The splitter may not be the problem causing your issue, but I would still suggest getting it replaced.

At this point all I can suggest is to call and ask for a technician. Tell the you have already troubleshooted most things. You might want to schedule it a few days out so you can contact your landlord or maintence person for the complex incase they need to work together, or get into some kind of wiring room. 

Any problems with your cable TV? Snowy picture or black squares or tiles on some channels?

I sent a email to  cox.help@cox.com 

dont have cox TV anymore but when i did it was really poor quality tiles on most channels

Still having connection problems got a tech scheduled for tomorrow thanks for all the help.

Tech just finished look like it was a 8 way splitter in there box outside 

now signal is

Connection

if it keep dropping ill call again next step is replace all the cable i hope its fixed

Those signal levels are much better. Really good upstream power level, which is sometimes hard to get. 

Flindrake said:
LockedQAM2561075360 Ksym/sec873000000 Hz-4.5 dBmV33.9 dBDOCSIS

This concerns me though. Your SNR should not be so low when a power level of -4.5. There could be some ingress (bad signal leaking in) in the 873Mhz range. If it acts up again that would be the next think I would suggest having a tech look into.

Well i am still disconnecting 4th time now after tech's visit

Connection

Here is the event log as well 

Event Log

he did not use a meter to check signal of the cable wire he only removed a splitter that was in there equipment box outside

will probably call them again tomorrow 

2nd Tech just finished said there are some errors coming from there box outside and it needs repair, he also changed the port for my internet and signal is now

Connection

He also said that if after the repairs if it still happens to return the gateways and get a new one (un refurbished)