5 points : Lyrics/Tempo/Pitch/Pronounciation/Feel.
i think your main problem is pronounciation and feel. (sounds you're too distracted from focusing) feel wise it's pretty dead i'm sorry. you're not thinking about that person hard enough. hahah.
pronounciation parts like what sage has mentioned, if the lyrics go "I've been thinking about you" , and all I'm hearing is " ahbintcinginabaot you"
* = flaw points
I* + 've* = 've missing. you're lacking emphasis on "I" (Ai) when I only hear "Ah" than "Ai"
bee*n = you got more "n" than "ee", switch them around, more "ee" emphasis, and make the "n" almost silent. so it sounds more like you're saying "binn" than "been"
th*ink*ing = most of us have the "th" pronounciation problem, open your mouth a little, tuck your tip of tongue in between your teeth and try blow air through the gaps of your teeth/tongue. then retract your tongue. yours sound almost like "cingin" or "tingin"
your "k" is missing and you pronounced it as a G, you pronounce more "ing" than "kin" , if you read the words "tingin" it don't make sense, if you read it as "thinkin" , at least all it's missing is a "G". remember to make the ending "n" (of thinki[n]) a silent "n" so you don't go "thinkinnnnn" like your beennn problem.
"abou*t" = yours is "abaot" when the exaggerated (in a good way) pronounciation to get lyrics out there is "abaowt" , as you read this now, say the words "Ah Woo" , more emphasis on the "W" , so your lips form from an "AH" to a small circle gap of your mouth. now put that into "action" , Er(silentr)+Ba-ow-t. less A, more ow.
you's fine, some people see "aboutchu" (about you) you have them nicely seperated "About.you" . matter of preference. but if you're gonna use aboutchu, remember to keep the "ch" silent. thats the common problem when ppl literally pronounce CHOO.
listening to the remaining of the lyrics when you say "teeth" , I guess you don't have a "th" problem, just went careless at the others. "teeth are over there" , your "th" in "there" needs more "th" than silent "th" . there's too many to pinpoint out, but I believe you understand sometimes singing is very exaggerated english but that's what makes it catchy sometimes (of course don't over do it).
review every word you sing, and review every bit detail of the "start of word" / "center" / and "ending" . as i've pinpointed above. soon it'll be a good habit and you won't have a problem.
recently I recorded a vocalist with a lisp problem and this similar habit and another bad one to join words together. don't think he'll mind me posting the situation because we're all learning here.. the lyrics goes "as days pass I'm gonna love you more"
so what do you get when you join them up in a "slur" ? "esdespasmgonnelove you more"
if you don't pay attention at first like I did, it may sound like "active spasm goner love you more" hehe.
hope this is of help
80¢ worth