Ubuntu – Ubuntu 16.04 doesn’t recognise wireless card after a while

I've just installed Ubuntu 16.04 along with Windows in a dual boot. I have an HP Pavillion dv6000 with an Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection and my driver is iwl3945. Even on my first try to boot Ubuntu the sign on the wifi sign blinks from red to blue, which is a sign that my internet connection is not stable. After a while, I lost Internet connection completely(even wired one) the WiFi sign is now constantly red.

However, the sign up and right of the screen still shows I have Internet. If I switch off the WiFi switch and then switch it on again,it shows no enable wifi option(in fact I cannot select it).

Please do you have any idea? No matter how much I've searched on the Internet I couldn't find something helpful. I'm new on ubuntu so please be lenient.

Here is the output of the lspci -nnk | grep -iA2 net

02:00.0 Network controller [0280]: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection [8086:4222] (rev 02)
Subsystem: Hewlett-Packard Company PRO/Wireless 3945ABG [Golan] Network Connection [103c:135c]
Kernel driver in use: iwl3945
Kernel modules: iwl3945
08:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd.       
RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller [10ec:8136] (rev 01)
Subsystem: Hewlett-Packard Company Pavilion dv6700 [103c:30cc]
Kernel driver in use: r8169