i'm running sonar artist..but I am starting to get real problems with audio dropout...i'm using  a REALTEK sound card in a Lenovo desktop running windows 10..any help would be great.thanks.

I would suspect the Realtek PC sound "card" as they make poor recording devices.  Best option is to get an actual recording interface unit.  There are some relatively inexpensive 2 channel USB connected devices available.
Here is a very inexpensive "starter" type interface  https://www.sweetwater.com/store/detail/UMC22
 
Wi-Fi is known to cause PC sound problems such as dropouts.  Temporarily disable Wi-Fi and see if that helps. 
 
You can also run the free Resplendence Latency Mon and it may help to pinpoint problems.
 http://www.resplendence.com/latencymon
 

First you need to optimize your computer for audio streaming and use the utility Fireberd recommended to see what is causing dropouts. Most of use turn off Wireless Networks but there can be any number of processes running that steal away your CPU.
 
You can use your on board audio for pure midi and even a few audio loops, but as said your best experience is to use ASIO drivers with Sonar, ( that Behringer does not have ASIO drivers so actually won't help)
You can get a interface with asio drivers for as little as $80. But that's a whole other topic, visit our Hardware sub forum to find more info.
 
In the meantime, optimize your PC and try WASAPI exclusive driver mode. That's as good as it's going to be with a cheepo on board sound card.