Broken browsing through category links pagination.

I am new to wp.
This code returns a list of links pagination of a category.
The second time a user clicks the generated links then the functionality returns a page that does not exist.

eg.
The category link (first paginated page) is http://www.mypage.com/mycategory#all WORKS OK
the first click returns this link http://www.mypage.com/mycategory/page/2 WORKS OK
the second click returns this link http://www.mypage.com/mycategory/page/2page/3 NOT OK

Why the code removes #all but not page/2 from the link?
What am I doing wrong and how can I improve the code?

The code I used:

<?php
if($loop->max_num_pages>1){?>
    <?php
    for($i=1;$i<=$loop->max_num_pages;$i++){?>
        <a href="<?php echo get_category_link($category_id).'page/'.$i;?>" <?php echo ($paged==$i)? 'class="active"':'';?>><?php echo $i;?></a>
        <?php
    }
    if($paged!=$loop->max_num_pages){?>
        <a href="<?php echo get_category_link($category_id).'page/'.$i;?>">Next</a>
    <?php } ?>
<?php } ?>