Turning 30 next year and I am not sure what to do about relationships

I am turning 30 next April and since my undergraduate years (2005-2009), I have not been able to have a successful relationship. I do not know what to do anymore and it's really bothering me that I can not make it work. Most the relationships I have been in have not lasted longer then 4 months.I think my problem is that I am meeting the wrong kind of guys. I have tried to meet guys on OkCupid, Scruff, Growlr, Grindr, you name it and I always end up regretting it. Since I have had so many bad situations with people, I am finding it harder to want to meet anyone or go on dates with anyone. I don't know, I think I am trying to hard. But I just do not understand how anyone makes a relationship work.