should I leave my seven year relationship.

Hello ladies, you all are my second family so honest opinions please. I got myself in a long distance relationship almost seven years ago in which we are finally moving in together, I love him dearly and have always been loyal but have also been the more mature one since he is a year younger then me, he has made plenty of mistakes. I was not always perfect but I was always loyal and stuck around. Our relationship has improved greatly since we have grown up over the years, or so I thought. I have never had problems with him having female friends except for a select few that cross the line. This one female he met through his friend over the summer is extremely flirty and crosses the line with everyone even though she's married, but he lies to me about her. He said he doesn't talk nor Snapchat her. His friend has an online thing and I found it and she was in it and so was my boyfriend and they were chatting and she also said about snapchatting her back. This means he's lied to me yet again. I try being mature and looking past it because I love him and we have a place we're getting together this summer and he treats me well except for this lie. She is married but I still don't like the way she speaks to him and the way he lies about talking to her. I just can't do the lies when I'm an honest and understanding person. Only so much someone can take. Advice ?