PLEASE HELP! UNIQUE INTERNET PROBLEM

Hi, I will try to make this as short as possible. Few days ago My ISP which is Charter disconnected my internet due to a messup on their part on reciving monthly payment, anyway afrew a quick call, it was back on, however I started having very wierd lag problems with Skpe as I could hear other people speaking but when i talked they couldnt hear me, which was most noticable while Gaming online, I constantly get disconected from BadCompany 2 servers every 5 to 10 min and while i play Leauge of Legends my champion goes unresonpive for as long as 10 sec and When i type in chat it dosnt show up until the "lag" goes away, but no one else is effected by it, also that problem always usualy happns with Skype at the same time, also my xfire which usualy never used to get d/ced puts me offline, when I open images or videos they seem to lag drasticly and when i look at my modem all the lights are still blinking but Ive been also having complete modem resets that didnt use to happen before oftent lately as well .after calling my ISP ( charter) a few times they told me that they had recently upgraded to 18mpbs in my area and I might need to get a DOCSIS 3.0 modem and it should fix the problem, after switching my Motorola S5101 with one of their DOCSIS 3.0 modems , all the above problmes still presisted so i called them again and they send out a technician which just looked at all the wire connections outside the house and replaced some heads, but to no avail. I also run my modem thru a D-Link Wifi Router, however i already tryed runing the new modem directly to my computer and switching the wires still nothing changes.

that was basicly all the information I have so far, I Dono if its a problem with my computer or its a probem with Charter or there is a lose or a broken connections somwhere in the coaxial cable around the house or on the outside boxes, which already been checked by the technician. Im literaly going crazy trying to understand what is wrong with my internet, if anyone can help me I would be for ever gratefull.