It has been 4 years since I got married and sadly physical intimacy has drastically gone down. What should we do?

I think the mundane routine of life has got to you. You are bored and frustrated. My husband and I went through the same cycle after the birth of my daughter. Life became frustrating and we went through a phase where we did not want to be around each other. Lack of communication is the main culprit in such cases. So first try and spend time talking about what's bothering you and that will solve most of the problem.You need to find time for yourselves and have fun. Try revisiting the places you have been to where you had fun. Try things you have not done before....set date nights,watch erotic movies,get aways,etc.