Oh Hun, I am really feeling for you because you are ME 4 years ago!!! I felt my 3rd son was as perfect as a boy could get, didn't want another, unless it was a girl, and felt like a stupid failure getting around with another huge belly full of yet another boy- only this one unplanned, conceived while on birth control and breast feeding. It made it worse that everyone, including myself, thought and said "Well this surprise will be your longed-for daughter, that's why it happened!" At 20 weeks I found out he was a boy and had a mini-meltdown. I was angry because I hadn't had a chance to sway and felt like my body had played a nasty trick on me. My poor husband agreed to "consider" a 5th just to stop me having a full-blown breakdown I think! 2 weeks later I made him PROMISE to have a 5th so I could relax and move on with life, (God I sound like a crazy bitch when I actually type it all down!
I, too, wished I could go back in time and just not be pregnant, I wasn't motivated to eat healthily and wasn't excited about kicks, names, nurseries, etc. Fast forward 4 1/2 months and I gave birth to the most exqusite, precious bundle of boy ever, and I was madly in love at first sight. From then on, I would never have wished him to be anything other than the perfection he was. I can honestly say about 90% of it, for me, was the crazy pregnancy hormones. Everything was SO much worse when I was pregnant, when I had those hormones out of me I was a "normal" person again! Obviously I went on to have that 5th, but didn't quite feel the desperation I did while pregnant (until I WAS pregnant again, and turned into Godzilla again, lol!!)
Sorry for the long rant, but my point is- SO much of this is because of the pregnancy hormones rushing through your body Hun!!! Be kind to yourself, you are a good Mum! Just a bit stressed and down at the moment! I don't know if you have the option to go again, but if not, please trust me that you will feel SO much better in 3 months or so! You WILL fall in love with this special little guy, and he won't stop your special relationship with number 3. Just think of this baby as a "gift" to your 3rd son, of a best mate for life! Pregnancy is not all sweet roses, it is bloody hard physically & emotionally, better times and happy hormones await you! Good Luck Sweetie!!!