for true paragraphs (not line breaks) I do the following (assuming $text is the value of your paragraphs variable.
$text = nl2br($text);
$text = "<p align=\"left\">$text</p>";
$text = str_replace("<br />", "</p><p align=\"left\">", $text);
This effectively starts by turning \n newline characters into single line breaks, then it appends a paragraph tag to the start and an end para tag to the end, and then finally replaces all those lovely <br /> tags inserted by nl2br() into end para and start para tags.
Fortunately, most browsers will ignore an empty <p></p> tag, plus as you are replacing your generated <br /> tags and not any manually inserted <br> tags, your hand coded new line formatting will be retained. HTH