What is wrong with me?

Why at the suggestion that I have flaw...do I go into a total tailspin thinking thoughts that I am somehow completely defective? Yesterday it was the thing with my friend...that had me pondering all evening and just now...a coworker just blurted out while we made small office chit chat..."Are you alright?". She said it like she had to muster up courage to ask me...I responded with a "im fine" and when she looked like she didnt believe me...I felt compelled to add, "I'm a little tired...but I'm good". Totally unnecesary but she really threw me off. I dont feel bad or off at all. Actually with the morning sickness and mood swings...today is a GOOD day. And I could have just dismissed it, as is probably appropriate...but instead I am thinking...what is it about me that has her wondering am i alright? She said I didnt seem like myself...(does she even know me tho? Hell naw) But anyway...I am seriously feeling myself getting anxious and my mind is thinking too many things too fast...WHY did she feel compelled to ask me that? Am I alright? I am over here asking my SELF if I'm alright? As if I wouldnt be the first to know if I wasnt...SIGH! What is going on? Why am I letting 'things' that other people say...make me doubt and question myself? And why am I wasting my precious time and energy worrying about it? I guess I am feeling a bit insecure lately...I have to do something about this...cuz I cant go thru this every time someone decides to let me know what they "think" to be true about me. I just cant!