Leo, your Mars in the 7th house of marriage in Cancer shows a certain amount of tension. In a man's chart, a poorly aspected Mars in Cancer can indicate a man who has difficulties with women generally, because the problems started with his feelings about his mother. I wonder how your husbands got along with their mothers?
Also, Mars shows your own assertiveness and aggression. I am not saying you are an aggressive person, because everyone has Mars in her chart somewhere. But yours is square Pluto, suggesting a propensity to get involved in bitter power struggles. The alternative reading of the 7th "house of marriage" is "the house of open enemies"--which surely describes a lot of difficult marriages. Possibly whenever your husbands did something or said something you didn't like, your really got angry.
Your 7th house is ruled by your moon in Pisces, in the second house that includes your money and personal possessions. Possibly you argued about money, as your moon looks pretty stressed.
One thing to keep in mind is that your sun is in the sign of Leo. Leos are royalty. They can become unhappy if others do not understand that, but a true "queen" knows who she is regardless of how badly others behave, and therefore can afford to be generous towards others' failings. With your sun in the 8th house, you may be a very private person who prefers to keep to herself, especially if she feels wounded, but it is important for you to get out and in circulation with other people.
Just now Neptune is opposing your sun/Mercury and approaching your moon, which is very hard on your feelings, self-esteem, and positive sense of identity. Although "this too shall pass" possibly the best use of this transit is to consider how you might shed any aspects of your personality that truly do not support you as you experience this difficult phase of your life.
Your north node of personal growth is in your 7th house of marriage. I don't know whether it is possible or desirable to mend your relationship with your husband, but learning either how to find a supportive relationship and how to adapt your self to the give-and-take and compromise that marriage requires should be beneficial to you.
Will you "ever be happy"? You can be happy this very moment once you realize that you are in charge of your emotions, and do not look outside of yourself to other people, a job, or your material circumstances to make you happy. Focus on the good things in your life that you can experience each moment. See if you can get hold of the book The Power of Now by Eckhart Tolle.
You also have to think of what kind of adult role you are modeling for your daughter. If she sees you as constantly anxious and depressed, she can grow up thinking this is normal, and become the same way. Is this what you want for her? Wouldn't it be better to show her that you and she are strong, confident women, no matter what hardships life throws your way?
Good luck with your exams, Leo.
