Hey Doctor I’ve Had This Ache Like Pain That Has

Question: Hey doctor I’ve had this ache like pain that has a feeling of pressure which sometimes feels like it’s burning in the lower left side for almost 2 weeks now, I have attached an image of the location. It’s mainly worse if I’m sitting up on a chair or if I’m moving my abdomen around a lot. At first I thought it may have been appendicitis but I read that the pain for that originates from the right side and develops quite quickly? Then I thought it may be my IBS i have had stomach problems for about 2 years but I have ruled out anything serious through testing. The pain however it’s more of an achey pain so I’m thinking it’s a muscle related problem because for the first time a couple weeks ago I started having sex and it has been pretty regular I’m quite a skinny as well and weak and those muscles down there I haven’t really used before. Could that possibly be the reason for the pain I’m just finding it hard to heal and get better and it seems to be getting a little worse what do you think is there anything I should be doing to rule it out being not muscle related I’m seeing a physio today should I see my gp again also? I did notice a lump around the same area and my gp felt around and did an ultrasound but it turned out to just be a vein so there’s no hernia or anything like that.