falling back taking steps forward repeat

Every time I think I'm doing better being happier I fall right back down. Nobody really understands how hard it is for me to make a step and be a little happier than I was yesterday. I just keep getting thrown back down and repeat the process. My life isn't hard I have a wonderful life I'm a stay at home mom to 3 beautiful children, I'm married to a very hard working man and we are expecting our 4th child. Sometimes I just feel stressed and overwhelmed even though I don't do much . Anyone else