I removed your full IP from your post just to be safe. As mentioned the IP itself belongs to OVH, which offers DDoS protection, but it's quite likely you subscribe to services via one of their many (many) resellers. I would first inquire with your provider immediately as to what the options are for mitigation service. They can probably add this to your VPS for an additional monthly cost.
You may also wish to temporarily place your site behind CloudFlare though that will do little/nothing if they're attacking the server IP and not the hostname, which is likely, so unless you add to Cloudflare and change your IP and not leak the new IP (usually found in mail headers) then it will be pointless.
You may also wish to seek services with a provider that specializes in DDoS protection. Several advertisers on vpsBoard offer this and you can also find a VPS in the offers forum as well that come with DDoS protection.