How can I say "孤陋寡闻" in English? In a situation like:

My friend: 你知道StackExchange吗?
Me: 不知道啊, 孤陋寡闻了. 

how can I properly translate 孤陋寡闻了 here? "I am being ignorant"?
你知道 StackExchange吗?
You know StackExchange?

不知道啊, 孤陋寡闻了。
Nope, I'm so out of touch.