Messages issues are killing me .. am i the only one?

Hello,
i actually have an issue with my whatsapp and i have googled it many times but found nothing about it. i really need to know how to fix it because it is nerve-wrecking, confus and causing me problems sometimes.

The issue is with the messages:
* Sometimes i send message and i get one tick and the message doesn't make it to two ticks
* Sometimes i send messages and i get two grey ticks but the other device doesn't receive them.
* Sometimes someone sends me a message and gets two grey ticks but my device doesn't receive it
* Just minutes ago, someone sent me a message that i received, read, and replied to, and He still has two grey ticks
(although the previous and the following messages have blue ticks)

Now what is it? Is it my phone? Is it whatsapp? And am i the only one who is facing this?

P.S: i have restored my phone's factory settings two days ago and currently have the latest version of whatsapp, the issue was there before that procedure and remained after it .. plllllleeeeeease help me

Thanks in advance,

Aya

— modified on Dec 4, 2014, 1:23:56 AM