18th week is too early to feel continuos movements

Please read these articles..<a style="text-decoration:none" href="http://app.babychakra.com/article/3171"><b><font color="#3b5998">Fetal Movement Week By Week: What To Do When Movements Reduce, What Is Normal And What Is Not</font></b></a>

Yes it's normal.. initially you will not feel baby movements all the time afterwards they; become regular

Yes it is normal dont worry. Somedays baby is more active than others. Movements will get more regular in coming weeks