I use Bootstrap 3.3.7, and it’s hard for me to get a search box and a button to drop the text under the heading when viewing on a small screen.
I would like it to add up as follows:
Big screen (as at present):
[Title] [search input] [submit button]
Smaller screen:
[Title]
[search input] [submit button]
Small screen:
[Title]
[search input]
[submit button]
Any help is greatly appreciated. I have been for this for ages, and my CSS skills are not enough for me to make any decent progress. Thank.
Big screen:

Smaller screen (button turns off):

Small screen:

Here is my code:
<nav class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
</div>
</nav>
<div class="container" role="main">
<div class="page-header">
<form action="" method="GET" class="form-inline pull-right">
<div class="form-group form-group-lg has-feedback">
<label class="sr-only" for="search">Search</label>
<input type="text" class="form-control" name="q" id="search" placeholder="Search">
<span class="glyphicons glyphicons-xl glyphicons-group form-control-feedback"></span>
</div>
<button type="submit" class="btn btn-lg btn-success">
<span class="glyphicons glyphicons-search" aria-hidden="true"></span>Search
</button>
</form>
<h2>Quite Long Header Text</h2>
</div>
</div>
Update
Thanks @Robert C. Here's how it looks with your suggestion:

and

and

, , . , , . , .
, , ?