Pregnancy becoming tougher day by day.

I'm 27 weeks pregnant and have gained 15 kgs till now. Most people say I am huge than expected. It has become difficult for me to walk or get up from the floor. But during night its even more worse, I am not able to change sides because it causes extreme pain down there. I become restless. Also I try to sleep on my left side but that makes me even more uncomfortable. I talked to my gynaecologist about it but she didn't consider it as an issue and told me it happens during pregnancy. Please tell me what to do and is it important that I sleep on my left side always?