Oh yes, pregnancy is a riot! I think if we didn't get something so wonderful out of it at the end the human race would cease to exist!!!
My 2nd tri went really quick, so i expect you'll be in the 3rd before you know it.
Sorry to hear you're feeling low (just read your other post) I think your hormones are playing a big part in how you feel and how you perceive things. As you've still got half your pregnancy to go through, it probably feels like meeting your baby is so far away it'll never happen and as you don't have that distraction yet, you're feeling the loss of your horse even more (I love horses too - wish I never gave up riding) but when you're holding your baby and are looking after him/her you won't feel the void so much.
An old friend of mine went throught exactly the same as you several years ago. She had always been surrounded by horses and doted on hers but when she became pregnant she had to sell him, she couldn't afford both, and she was heartbroken but once her little bundle arrived she said it put it in perspective and she wouldn't change it for the world.
Can you still see your horse at all? I know its hard at the moment but it'll get easier with time and just think when your babes older, you'll be able to get another horse and teach him/her how to ride
Take care hun and I hope you do feel brighter soon. (Always here if you need a chat!)
Nicki.x