Advice Needed Please!!!!! My wife complains that sex with me is too painful

Hello H.O.O blog readers, there is a problem that needs a solution.  Please married people and relationship experts we are counting on you. Read below.

My wife and I have been together for more than three years. The sex at the beginning of our relationship was regular and extremely fulfilling, but at some stage, our problems began. She complains that I am too large for her. Sex is once a month, painful for her and consequentially embarrassing for me. I try to avoid penetration but she insists on it though I am aware this is sacrificial on her part.

Please drop solutions or advices below. Thank you.