Sudden weight gain and bloating

I am a 45 year old white woman who began menstruating at age 17, later than other girls my age due to being athletic. Over the past 6 months or so, I've gained about 10 pounds. Although my job is sedentary, I am moderately active and try to do some form of physical activity every day or other day at most. Unfortunately, due to an injury, I cannot due any high impact activities so I do a lot of walking and yoga. All my life I've had an apple body frame e.g. small breasts, small waist, weight gain in my butt and legs. However, this newly added 10 lbs seems to be mostly in my belly which feels HUGE and uncomfortable. I feel like I'm going to explode. Even sitting feels uncomfortable; like there is a line right below my breast bone where my belly is bulging out. I realize that my eating habits the past 6 months have not been as rigid as I typically held myself to, so maybe 5 lbs would not have been a big shock. This feels very different. Today I ate what most people would consider to be a normal lunch of modest proportions. Afterwards and now, over 6 hours later, I feel completely bloated and very much like I'm going to blow up. I am completely distraught. Friends tell me that these are signs that I am perimenapausal. Is that true? Are these typical signs of peri menapause? My mother didn't even start to have symptoms of menapause until she was in her 50s, so I find this surprising. I've also noticed that, as hard as I try to work out and cut the calorie intake, I can't shake a pound. I am incredibly depressed and need help and answers. If anyone has any advice or insight, please, please post.

Thanks. Gracie. :-( :-( :-(