Search Results: hiding a secret

My girlfriend has introduced me to many of her female friends, and she tells me when she is going out with them.
On the other hand she never talks about her male friends or mention their names, which I find it strange because she has lot of male friends, and they all are kind of her type, poets, writers, film makers, etc.
For example there is this one guy she kept texting 2 days ago while we layed in bed. She was reading this long message of someone called Sean, when she notice me looking she quickly put her phone down like she was hiding something, after a while she was on whats up app, and the name Sean was on top of the list recent texts. I was intrigue so I done a little research on social media i find out the their are firends on facebook, instagram, and that recently she been liking a lot of is posts. She invited me to watch a play written by some friend, I find out using social media that Sean is the friend she mention.
Recently she is spending less time with me, its also been a while since we spend a full weekend together, and all this texing guys that she dosent tell me about, kind of make me thing something shady could be going on. Im not the jealous type, but Im also not a full. I wish I could talk to her about this, but that won't be possible because she usually gets extremely defensive and agressive, everytime I question her secret life. Recently we been having much less sex, and usually says that she's too tired to do it, or she will stop in the middle of it, saying it feels unconfortable. Please guys give me your honest opinion?