extend unallocated disk to an existing lvm

extend unallocated disk to an existing lvm

ubuntu server is running on VM, initial setup was to have 10GB size, then increased it to 5GB, total of 15GB.
root@media:~# pvscan
PV /dev/sda5   VG media   lvm2 [9.76 GiB / 0    free]
PV /dev/sda4   VG media   lvm2 [5.00 GiB / 0    free]
Total: 2 [14.76 GiB] / in use: 2 [14.76 GiB] / in no VG: 0 [0   ]
above shows, extended lvm to 15GB.
Few days later, i added another 15GB, total of 30GB as seen below:
Disk /dev/sda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders, total 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0002948a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      499711      248832   83  Linux
/dev/sda2          501758    20969471    10233857    5  Extended
/dev/sda4        20969472    31457279     5243904   8e  Linux LVM
/dev/sda5          501760    20969471    10233856   8e  Linux LVM
when i try to create another partition out of /dev/sda, im getting below error
All primary partitions are in use
Adding logical partition 6
No free sectors available
how can i use my unallocated disk to extend my lvm? i cant seem to create a new partition anymore. is there a limit to it?