Enlarged 'boobs' in a dog almost always mean pregnancy/whelping....unless they are tumours or mastitis. But they can sometimes swell a little during 'false pregnancy' (a hormone upset in unspayed females.)
Like Margot said, twitching while sleeping is absolutely normal, and is usually associated with dreaming. If she's twitching while awake, that can mean itching, irritation somewhere, or pain.
If it's happening while she's awake, then that and the swollen mammary glands are cause for concern, and she needs to see a vet.
I have absolutely no idea. Is this a make or female dog? If a female, has she had a heat cycle? Any chance she was bred?
Twitching? You mean while it is asleep? That would not be abnormal.
If the dog seems off or I'll l, you should consult your Vet.