After 17 years of marriage and three kids, everything seems meaningless because of so many problems between us.
Mainly, my wife has a sick habit of thinking I'm cheating on her, though I've been faithful all these years.
I continue living with her only because of our kids, but I'm convinced that this relationship is going nowhere if she doesn't get help.
She doesn't accept that she has this destructive habit even though I've already left a couple of times, but I always returned because of my kids. She gets worse when she's having her monthly period.
What's better for the children: Living with both of us fighting and insulting each other, or living without this trouble, only with their mother?

- One Foot Out

Let me turn it around: What's better for your children - leaving them with a mother who regularly becomes suspicious and difficult, or helping their mother learn to understand her own moods, before making a decision about the marriage?
I understand your frustration, but it doesn't negate your continued responsibility to try to ease things, at least for your children's sake.
Approach your wife in between her periods and try to talk to her about getting more informed on a potential condition of Premenstrual Syndrome (PMS) or, Premenstrual Dysphoric Disorder (PMDD).
Your wife cannot be any happier than you are, with the current turbulent situation. If you show some compassion and caring for her to find help for what's driving her anxieties, it may not save your marriage, but it will surely improve your future contacts with each other and effects on the children.

• The symptoms of PMS can range from general moodiness to severe bloating and cramping. But some women experience a more severe form, related to PMDD, which can be very disruptive if left untreated.
Your wife should be discussing this possibility with her physician, for her own comfort and emotional health. (Do not deliver this information as something she must do for you or your relationship, but rather for herself).
While the signs of PMS include irritability and mood swings, PMDD symptoms are far more severe. They can include: a very depressed mood, feelings of hopelessness, anxiety, tension, mood shifts, persistent anger or increased interpersonal conflicts. These symptoms are present in the majority of months, and may be worse some months.
There are treatment options for PMDD, including stress reduction, undergoing therapy with a cognitive behaviour specialist, some medications, dietary changes and/or exercise.

I'm a very anxious, self-conscious 17-year-old girl who feels awkward in certain social situations, although I'm not exactly shy. I also suffer from low self-esteem. People have told me that I'm not very perceptive, that I'm immature for my age; even teachers have said they find me "weird" or abnormal. I've had an extremely difficult childhood, which may be still causing these problems. These issues are having a negative impact on my life and possibly hindering my development towards adulthood, including relationships and dating. How can I conquer these issues and move forward with my life?

- Lagging Behind

Be assured that any teacher who labelled you weird or abnormal was ignorant, lazy and unfit to teach. What matters is how you feel about yourself and what you're prepared to do to help yourself in areas you feel are holding you back.
Yes, your tough childhood surely played its negative part; but the fact you recognize this, is the first step on a path to putting it behind you.
I urge you to seek individual counselling with the goal of building your self-esteem. Your school guidance counsellor should be able to refer you to recommended psychologists or therapists; or a local community agency can refer you for counselling.
At 17, it's very important to start feeling good about yourself before venturing into the dating world and relationships. Understand that many people your age are also shy and anxious about forming such close connections; you are not alone in this.
But before you enter those situations where you need to use judgment about whom to trust, you need to work on your self-confidence, with professional help.
Once you believe that you are unique, special and worthy of honest, decent friendships and relationships, you'll have risen above those past experiences which were not your fault. And you'll be able to take charge of your future relationships with others.