Thank you for the additional information.
It sounds like the feelings from your childhood sexual abuse are affecting you. You mentioned feeling afraid of a nervous breakdown and also that you find it hard to cope with anything. Both of these feelings signal that you are overwhelmed right now.
I want to reassure you that you will not have a nervous breakdown. Having a nervous breakdown is a term that is used in general and is not an official diagnosis. You will not lose control or be unable to function. What you may be experiencing is anxiety, possibly related to the feelings you are bringing up about your past.
People who have been abused as children often develop Post Traumatic Stress or another anxiety related disorder. It comes from the trauma you went through. Most survivors are able to function well enough, but one day they find they begin to feel like they can't hold it together anymore. This usually happens when they are reminded somehow of the trauma. And since the trauma happened so long ago, the connection between how you feel now and your past is not easy to make. So you feel that you are losing it and are unable to cope.
You mentioned feeling like a volcano ready to erupt. This is your feelings coming out from what happened to you. Modifying your behavior in therapy is helpful, but the deeper issues still need addressed. By confronting what you went through and letting your feelings out in a safe and secure environment, you can work through your pain and feel whole.
Do you feel your therapy is helping you? If so, then you can talk with your therapist about this and get his assistance in working it through. But if therapy is not helping, you might need to try another therapist. You can find one through your doctor or by searching on line at http://therapists.psychologytoday.com/rms/.
You can also help yourself through learning more about being a survivor of abuse and how it can affect you. Here are some resources to help:
The Wounded Heart: Hope for Adult Victims of Childhood Sexual Abuse by Dan B. Allender
Hush: Moving From Silence to Healing After Childhood Sexual Abuse by Nicole Braddock Bromley
You may also want to consider support groups, either on line or in person. Getting support from others who feel as you do can make a big difference.
I know you feel overwhelmed. It is not easy to feel that you are losing control. But I can assure you that you are not. With some help and support you will get through this and feel better soon.
I hope this has helped you,