Esmi, thank you for the information. As of this morning, things seemed to go back to normal already and the pages are loading as usually.
Last night, there are times when I get message like “Error establishing Database connection” and then after that it would take unusually long to load up a page.
Before and after this issue, I did not make any changes in the site. The only thing is that yesterday I was getting a sudden increase of traffic due to Valentine Day and I was suspecting it to be the cause of it.