Rectal Pressure?? 39 weeks

39 weeks today with our second planning a home birth and I'm wondering if need to call our midwife. Since around 2pm I've been having consistent rectal pressure (like I need to poop but I don't) and it doesn't go away unless I'm sitting down. I've had a mild back ache today but thought it was just from doing too much laundry etc. I don't feel like I've had any contractions like I did with my first at all so I'm not sure if its just baby pushing down or if this is labour starting. Anyone else had a completely different experience with their second compared to first baby? Should I call my midwife just in case??