Have you tried to run Zertop's line test?
Never heard about it before but downloaded the Android app and here's my results.
Zertop's LineTool Results
Date/Time: Mon May 23 17:21:13 GMT+02:00 2016
Basic Report:
Your packet loss was 0%.
Your average ping was 58ms.
Your maximum ping was 155ms.
Looking at your average ping, your line seems to be a bit dodgy. This may account for any slow speeds you may be experiencing. However, it could just be related to a high-latency home network (eg... Wi-Fi). If you feel the need, please post the results (at the end of the program) into the forum for advice!
Detailed Report:
PING 155.239.255.250 (155.239.255.250) 56(84) bytes of data.
64 bytes from 155.239.255.250: icmp_seq=1 ttl=63 time=32.4 ms
64 bytes from 155.239.255.250: icmp_seq=2 ttl=63 time=27.6 ms
64 bytes from 155.239.255.250: icmp_seq=3 ttl=63 time=101 ms
64 bytes from 155.239.255.250: icmp_seq=4 ttl=63 time=45.2 ms
64 bytes from 155.239.255.250: icmp_seq=5 ttl=63 time=26.8 ms
64 bytes from 155.239.255.250: icmp_seq=6 ttl=63 time=33.7 ms
64 bytes from 155.239.255.250: icmp_seq=7 ttl=63 time=50.4 ms
64 bytes from 155.239.255.250: icmp_seq=8 ttl=63 time=38.6 ms
64 bytes from 155.239.255.250: icmp_seq=9 ttl=63 time=53.6 ms
64 bytes from 155.239.255.250: icmp_seq=10 ttl=63 time=69.1 ms
64 bytes from 155.239.255.250: icmp_seq=11 ttl=63 time=31.4 ms
64 bytes from 155.239.255.250: icmp_seq=12 ttl=63 time=52.0 ms
64 bytes from 155.239.255.250: icmp_seq=13 ttl=63 time=28.5 ms
64 bytes from 155.239.255.250: icmp_seq=14 ttl=63 time=155 ms
64 bytes from 155.239.255.250: icmp_seq=15 ttl=63 time=76.4 ms
64 bytes from 155.239.255.250: icmp_seq=16 ttl=63 time=48.1 ms
64 bytes from 155.239.255.250: icmp_seq=17 ttl=63 time=79.9 ms
64 bytes from 155.239.255.250: icmp_seq=18 ttl=63 time=26.0 ms
64 bytes from 155.239.255.250: icmp_seq=19 ttl=63 time=30.0 ms
64 bytes from 155.239.255.250: icmp_seq=20 ttl=63 time=31.8 ms
64 bytes from 155.239.255.250: icmp_seq=21 ttl=63 time=64.8 ms
64 bytes from 155.239.255.250: icmp_seq=22 ttl=63 time=57.0 ms
64 bytes from 155.239.255.250: icmp_seq=23 ttl=63 time=135 ms
64 bytes from 155.239.255.250: icmp_seq=24 ttl=63 time=45.6 ms
64 bytes from 155.239.255.250: icmp_seq=25 ttl=63 time=50.1 ms
64 bytes from 155.239.255.250: icmp_seq=26 ttl=63 time=57.0 ms
64 bytes from 155.239.255.250: icmp_seq=27 ttl=63 time=33.4 ms
64 bytes from 155.239.255.250: icmp_seq=28 ttl=63 time=112 ms
64 bytes from 155.239.255.250: icmp_seq=29 ttl=63 time=48.1 ms
64 bytes from 155.239.255.250: icmp_seq=30 ttl=63 time=114 ms
--- 155.239.255.250 ping statistics ---
30 packets transmitted, 30 received, 0% packet loss, time 29143ms
rtt min/avg/max/mdev = 26.032/58.590/155.006/33.324 ms