I would get a secured host, if your getting hit with DDoss attacks on a regular basis. You cant really "stop" a ddoss attack, since its basically nothing more than flooding your site with fake visitors until it cracks, and the server times out.
A good host can help. They will "null route" you when your getting hit, so your server doesnt go down for any longer than it needs to (an unblocked ddoss can cause real problems, and hours of down time.)
A cheap solution, which will *help* is to protect your site with Cloudflare.com. Spring for the $20 package after you get comfortable. It basically blocks known attackers (Usually "botnets", which consist of machines infected with malware.) and provides a sort of layer or door before your site to keep it safe.
They also provide a "Backup" so when they block everything out of your site, or if it goes down from the ddoss, users can still browse a cached version of the site.
-Xrm