It helps to try to put yourself in Mr. Rochester's shoes. Imagine marrying someone who turns out to be violent and dangerous, and completely insane. Your life with this person is totally miserable; it is like living with an animalistic stranger. But, you are married to them, and feel an obligation to take care of them because you said that you would, and her family isn't very helpful. Insane asylums are cruel and inhumane places, so you don't really want to put your spouse there. So, you are imprisoned by your obligations. You can't live life normally. You can't bring people to visit for fear your spouse might cause havoc. You can't socialize or have too many friends. And, you are incredibly lonely.
Mr. Rochester escapes his house whenever he can, because it reminds him of his awful situation. When he is home, he feels trapped by his circumstances--unable to break free from his duty and sense of moral obligation, yet also unable to find any joy in your station in life. Then, enter the young and charming Jane. He falls in love with her. For most people, this is a good thing, but for him it must have been torment because he knew he couldn't have her. First of all, he's married, and secondly, she is a highly moral person who would balk at the truth. He feels trapped--he can't tell her, he can't have her. His affection for her probably makes his situation even worse, putting additional pressure on him.
Rochester is imprisoned by his circumstances, and it isn't until Bertha's drastic actions that he is truly set free. But by that time, he feels that it is too late, and that his circumstances, having lost Jane, will leave him forever alone in his ruin of a life. I hope that those thoughts helped; good luck!