Locked out of my site

Hi There

I am having huge difficulties with my website. Originally I was having memory issues getting internal 500 messages amongst other memory issues. I changed the php script memory from 64 to 256.

Now when I upload the plugins, the site works ok and then once I havent used the site in a while and log out I cannot log back in. It just redirects to the coming soon page?

What could be the issue? Too many plugins?