iphone - Load more at the top of uitableview -

i need load more cell @ top of table populated custom cell, first time populate table ok, no overlap , no problem, if try load more cell cell appear wrong height , if try scroll cell change position randomly! code, mistake you?

- (nsinteger) tableview:(uitableview *)tableview numberofrowsinsection:(nsinteger)section {      return [self.arraymessaggi count] + 1; }  - (uitableviewcell *) tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath {      static nsstring *cellidentifier = @"cell";      uitableviewcell *cell = [tableview dequeuereusablecellwithidentifier:cellidentifier];      if (indexpath.row == 0) {          if (cell == nil) {             cell = [[uitableviewcell alloc] initwithstyle:uitableviewcellstyledefault reuseidentifier:cellidentifier];              uilabel *labelload = [[uilabel alloc] initwithframe:cgrectmake(0, 0, 320, 44)];             [labelload setbackgroundcolor:[uicolor clearcolor]];             [labelload settextalignment:nstextalignmentcenter];             [labelload settext:[nsstring stringwithformat:@"%d - load more...",indexpath.row]];             [labelload settext:@"load more..."];             [labelload settag:3];             [cell.contentview addsubview:labelload];         }          uilabel *labelload = (uilabel *)[cell.contentview viewwithtag:3];         [labelload settext:[nsstring stringwithformat:@"%d - load more...",indexpath.row]];      }     else {          if (cell == nil) {             cell = [[uitableviewcell alloc] initwithstyle:uitableviewcellstyledefault reuseidentifier:cellidentifier];              pfobject *obj = [self.arraymessaggi objectatindex:indexpath.row - 1];             pfuser *user = [obj objectforkey:@"dautente"];              float height = [self getstringheight:[obj objectforkey:@"testomessaggio"] andfont:[uifont systemfontofsize:13]];              uilabel *labeluser = [[uilabel alloc] initwithframe:cgrectmake(20, 10, 280, 20)];             [labeluser setbackgroundcolor:[uicolor clearcolor]];             [labeluser settext:[user objectforkey:@"username"]];             [labeluser setfont:[uifont systemfontofsize:13]];             [labeluser settag:1];             [cell.contentview addsubview:labeluser];          }          pfobject *obj = [self.arraymessaggi objectatindex:indexpath.row - 1];         pfuser *user = [obj objectforkey:@"dautente"];          uilabel *labeluser = (uilabel *)[cell.contentview viewwithtag:1];          [labeluser settext:[nsstring stringwithformat:@"%d - %@",indexpath.row,[user objectforkey:@"username"]]];       }      return cell; }   - (cgfloat)tableview:(uitableview *)tableview heightforrowatindexpath:(nsindexpath *)indexpath {      float height = 44;      if (indexpath.row > 0) {          pfobject *obj = [self.arraymessaggi objectatindex:indexpath.row - 1];         nsstring *text = [obj objectforkey:@"testomessaggio"];         height = 30 + [self getstringheight:text andfont:[uifont systemfontofsize:13]] + 10;     }      return height; }  - (void) setpulldowntorefresh {      refreshcontrol = [[uirefreshcontrol alloc] init];     [refreshcontrol addtarget:self action:@selector(aggiornatabella:) forcontrolevents:uicontroleventvaluechanged];     [self.messagestableview addsubview:refreshcontrol];  } - (void) aggiornatabella:(uirefreshcontrol *)myrefreshcontrol {      self.arraymessaggi = [nsmutablearray arraywitharray:objects];     self.messagestableview = [[uitableview alloc] init];     [self.messagestableview reload data]; }