Am I overreacting?

Hi ladies.

Bit of a back story. I'm in a long term relationship for 14years. We have an almost 10mo son together. He's our miracle baby as I have PCOS and miscarried back in 2009 and was told the only way to achieve pregnancy is through fertility treatments. We landed pregnant by some miracle without any treatments.

My SO and I have been clashing a lot. I have been a SAHM and am going back to school next week. He works 8-4 mon-fri. There are only 3 other people in his office. 2 females and 1 male (his best friend and boss). One of the 2 females he seems extra flirty with and she is the same to all males. She has made comments that make me uncomfortable and I have voiced this to my SO. I find out that they go out to lunch together if I don't send him in with a lunch or if I send him with something he's not in the mood for. However he knows that I am available to go to lunch with him and he NEVER calls me. He will go on coffee runs with her etc. More so when his boss is on vaca or out for the day. Well I have voiced my opinion on all these things and he acts like he doesn't go to lunch with her anymore. Well today he forgot important papers in the car so around 11:15 I went to drop them off and wouldn't you know they are getting out of her car with a couple of grocery bags and lunch. He also seemed nervous when he spotted me. He asked what was wrong when he came to the car window but I told him I had to go (didn't want to get into it in front of his place of work). As I was driving home he texted me asking why I was angry. He seemed a little worried and had to text me to ask again. Wondering if I'm overreacting or not. Because I feel my blood boiling.

ETA: I was 4.5 weeks postpartum and met her twice. On the 3rd meeting I had ran by my SO's workplace and went in with the baby. He was making copies of the baby's birth certificate that I needed. Obviously I said hello to all his co-workers and he got busy with a client when I was getting ready to leave. So said woman held the outside door open for me and on my way out she said "he seems really frustrated and is getting annoyed easily at work, maybe you should start giving it up and take care of him at home". I was shocked that she felt comfortable to say something like that.

Also I had been waiting to have sex until my 6 week postpartum visit. But I was giving my SO oral every night. So I felt some type of way about her comment. Also it made me feel terrible because I was still not feeling myself and a lot of thoughts went through my mind such as is he complaining to her about our sex life? I cried all the way home. And then told him about it when he got home that night.

He told me she was inappropriate for saying something like that but she was probably joking. We have couples that we are friends with and I still wouldn't be comfortable making comments like that to them.

She then mentioned not too long ago that if she hit the lottery she told my SO that he wouldn't have anything to worry about because she would by our son a house. WTF?! Who says that? She also will bring in food for him and he says she brought it for the whole office etc. But sometimes he'll bring the leftovers home and eat it when it's something he wouldn't have liked if I had made it.

She also had a same day surgery done back when my son was like 4-5 mo. He was sending her pics of our baby and telling her to get well soon. I'm so confused.

I am more concerned about the lying. And I have no problem if he has female friends. However there is a concern when you have to lie about things. If you didn't feel some type of way with her then why lie about anything? Also are you leading her to feel some type of way for her to be making comments about the future of our son? Or why are you sending her pics of our baby? He doesn't send his other female co-worker pics like that. Also just last week I said "I would like a little more respect from my SO and not have him flirt with other women." He never denied flirting. He just never said anything back. But wouldn't he have said "you're crazy, there's no flirting. I don't do that with anyone." Or "why would you even think that?". No instead he just replied back over an hr later saying he didn't respond because he didn't want to upset me more.

They always say "women's intuition" or "follow your gut". But he makes me seem crazy. So before I voice how I feel yet again, I needed some other opinions.