Dealing with Sadness

My husband and I met while we were both on the rebound and were both doing a lot of partying which continued far too long into our married life. We both did quit our bad habits however in the following years I focused on the kids and their activities and he worked more hours. Now all the children have moved on and I continually feel alone in a house with 2 people. We don’t share any common interests and I think the love has gone out of the relationship for me. I am afraid beyond comprehension of making a wrong decision and asking for a trial separation. I did once before and was met with an ultimatum so I backed off. The economy is one of the reasons for my choice as I don’t earn enough to support myself. I have also been through periods of anxiety and depression and because I am going through perimenopause I have experienced many ups and downs in my energy and moods. My father also suffered from major depression.
At times I feel so overwhelmed with sadness that I think I need to be alone to sort out things. The next day I may feel better. I am afraid that once I make a decision that there will be no turning back. I question myself so much. Am I being immature and expecting too much? How can I know the answer? I realize this isn’t a yes or no situation but I need guidance as I feel my health is suffering. I have no zest for life anymore. I am too far into the forest to see the trees. Please help.