Gosh it could be a wide variety of things. Anything from stress, to perimenopause, to being PG it's just hard to say. For me I have these symptoms and I am going through perimenopause. It can mimick pregnancy. I am 44 and have had the roughest 4 years of my life. I became hypothyroid when I was 40. I was always trim and I have put on 30 pounds. I blame it on alot of things. But I definately know that my metabolism has slowed down.
As far as pregnancy,,it sounds like you have your basis covered. It sounds more like pms symptoms. If your body hasn't already showed signs of hormonal changes going on I would be suprised. Usually by mid 40's alot of changes are going on. Good luck! Pregnancy might be alot nicer thing that the menopause thing. lol At this point I might opt for that.
P.S. Tender breasts are a big sign of hormonal changes, so are the sleep changes....Insomnia is something that happens throughout the month. 7 pounds is nothing. I would trade you in a heartbeat. You are very fortunate to have remained so thing clear up to 45. Most of us don't.